(navigation image)
Home American Libraries | Canadian Libraries | Universal Library | Community Texts | Project Gutenberg | Children's Library | Biodiversity Heritage Library | Additional Collections
Search: Advanced Search
Anonymous User (login or join us)
Upload
See other formats

Full text of "Drilling and preparation of reusable, long range, horizontal bore holes in rock and in gouge : final report"

rt No. FHWA-RD-75-95 



TE 

662 

»jj- A Lung and preparation of reusable, 

ru- ~ IG RANGE, HORIZONTAL BORE HOLES IN ROCK 

I "" *» O 



iriiO IN GOUGE 

Vol. I. State-of-the-Art Assessment 

).C. Harding, L.A. Rubin, and W.L. Still 



Dept. of Transportation 



JUN 14 1976 



Library 




Sr ATEi O* 



October 1975 
Final Report 



This document is available to the public 
through the National Technical Information 
Service, Springfield, Virginia 22161 



Prepared for 

FEDERAL HIGHWAY ADMINISTRATION 
Offices of Research & Development 
Washington, D.C. 20590 



NOTICE 

This document is disseminated under the sponsorship of 
the Department of Transportation in the interest of 
information exchange. The United States Government 
assumes no liability for its contents or use thereof. 

The contents of the report reflect the views of the 
contracting organization, which is responsible for the 
facts and the accuracy of the data presented herein. 
The contents do not necessarily reflect the official 
views or policy of the Department of Transportation. 
This report does not constitute a standard, specifi- 
cation, or regulation. 



FHWA DISTRIBUTION NOTICE 

Sufficient copies of the report are being distributed 
by FHWA Bulletin to provide a minimum of four copies 
to each regional office, two copies to each division 
office, and four copies to each State highway agency. 
Direct distribution is being made to the division offices. 



Technical Report Documentation Page 



-RD-75-95, 



3. Recipient's Catalog No 



id Subtitle 

Drilling and Preparation of Reusable, Long Range, 
Horizontal Bore Holes in Rock and in Gouge. Vol. I 
State-of-the-Art Assessment, 



5. Report Dote 

October 1975 



6. Performino Or 



7. Author's) 

J. C. Harding, L. A. Rubin, and W. L. Still 



I. Performing Orgo 

HWA-7443.1 



3n Report Nc 



9. Performing Organization Name and Address 

Foster-Miller Associates, Inc. 

135 Second Avenue 

Waltham, Massachusetts 02154 



10. Work Unit No. (TRAIS) 

FCP 35B2-042 



II. Controct or Grant No. 

DOT-FH-11-8486 



12. Sponsoring Agency Name and Address 

Department of Transportation 
Federal Highway Administration, 
Office of Research and Development 
Washington, D. C. 20590 



13. Type of Report and Period Covered 



Final Report 



14. Sponsoring Agency Code 



15. Supplementary Notes 

FHWA Contract Manager: Dr, 
Subcontractor: ENSCO, Inc., 



Steven I. Majtenyi 
, 5408A Port Royal Road. 



Springfield, Virginia 22151 



16. Abstract 

The objective of this study is to assess horizontal drilling as an alternative 
to pilot tunneling in geological investigation prior to the design and construction 
of highway tunnels and to identify means to increase the penetration capability 
and accuracy and decrease the cost of horizontal drilling. 

This volume assesses the horizontal penetration capabilities of available 
drilling equipment. The drilling of horizontal holes to a maximum length of 5000 
ft. (1524m) is found to be technically feasible and to offer an order of magnitude 
cost reduction over pilot tunneling. Limitations of present day equipment and 
techniques are identified and means to overcome these limitations are indicated. 

This is the first of three volumes. Volume II is published as FHWA-RD-75-96, 
subtitle: Estimating Manual for Time and Cost Requirements. Volume III is 
published as FHWA-RD-75-97 , subtitle: A Development Plan to Extend Penetration 
Capability, Increase Accuracy, and Reduce Costs. 



17. Key Words 

Horizontal Drilling, Subsurface 
Investigation, Highway Tunnel Design. 



18. Distribution Statement 

No restrictions. This document is avail- 
able to the public through the National 
Technical Information Service, Springfield. 
Virginia 22161. 



19. Security Classif. (of this report) 

Unclassified 



20. Security Classif. (of this page) 

Unclassified 



21. No. of Poges 

256 



Form DOT F 1700,7 (8-72) 



Reproduction of completed page authorized 



TABLE OF CONTENTS 

Section Page 

Table of Contents i 

List of Illustrations iv 

List of Tables viii 

1. Introduction 1-1 
LI Background 1-1 

1.2 Purpose 1-2 

1.3 Summary of Results 1-4 

1.4 Report Format 1-6 
Part I - Executive Summary 2-1 

2. State -of- the -Art Horizontal Drilling Capability 2-1 

2.1 Horizontal Drilling History 2-1 

2.2 Assessment of State-of-the-Art Horizontal 2-5 
Drilling Capability 

2.3 Limiting Factors in Horizontal Drilling 2-7 

2.4 Extending Horizontal Drilling Capabilities 2-10 

3. Planning Considerations 3_1 
3. 1 Background 3_1 

3.2 Site Selection 3_1 

3.3 Selection of a Drilling Method 3-2 

3.4 Drilling Costs 3_3 

3.5 Site Preparation 3_4 

4. Management Considerations 4-1 

4.1 Contracting Arrangements 4-1 

4.1.1 Lump Sum Contracts 4-2 

4.1.2 Mutual Risk Contract 4-2 

4.1.3 Time and Materials Contracts 4-3 

4.2 Contract Drilling Costs 4-3 

4.2.1 Fixed Costs 4-3 

4.2.2 Variable Costs 4-4 

4.2.3 Indirect Costs 4-4 

4.2.4 Risk Factor 4-4 



TABLE OF CONTENTS (Continued) 



Section 



Page 



Part II - Technical Discussion 
Systems Analysis of Horizontal Drilling 

Hole Specifications 

Functional Description 

5.2.1 Drilling the Hole 

5.2.2 Information Gathering 
Procedures 

5.3.1 Drilling the Hole 

5.3.2 Information Gathering 
Drilling Methods 
5.4.1 Prior State -of- the -Art Studies 



5.1 

5.2 



5.3 



5.4 



5.4.2 



State -of- the -Art Horizontal Drilling 
Methods 



Horizontal Drilling Methodology 



6.1 



Drilling Methods 



6.1.1 Diamond Wireline Core Drilling 

6.1.2 Rotary Drilling (Rolling Cutter Bits) 

6.1.3 Down-Hole Percussive Drilling 

6.1.4 Down- Hole Motor Drilling 

6.1.5 Continuous Core Drilling 

6.2 Chip Removal 

6.2.1 Selection of a Flushing Fluid 

6.2.2 Hydraulic Chip Removal 

6.2.3 Pneumatic Chip Removal 

6.2.4 Lost Circulation 

6.3 Hole Stabilization 

6.4 Borehole Guidance 

6.4.1 Factors Affecting Hole Trajectory 

6.4.2 Guidance Procedures 

6.4.3 Equipment 

6.4.4 Guidance Capabilities 



5-1 
5-1 
5-1 
5-3 
5-3 
5-5 
5-5 
5-5 
5-7 
5-9 
5-9 
5-13 

6-1 

6-1 

6-1 

6-20 

6-35 

6-43 

6-46 

6-48 

6-52 

6-54 

6-57 

6-57 

6-58 

6-62 

6-62 

6-67 

6-87 

6-104 



Section 



8. 





8.1 




8.2 




8.3 


Appendix 


A 


Appendix 


B 


Appendix 


C 



TABLE OF CONTENTS (Continued) 



6.5 Fishing 

6.5.1 Causes of Fishing Operations 

6.5.2 Prevention of Fishing Operations 

6.5.3 Fishing Tools 

6.5.4 Conclusions 

6.6 Sample Taking and Retraction Techniques 

6.6.1 Core Sampling 

6.6.2 Undisturbed Gouge Samples 

6.7 Water Pressure and Permeability Measure- 
ments 

6.7.1 Water Pressure Measurement 

6.7.2 Water Permeability Measurement 
Assessment of Horizontal Drilling Systems 

7.1 Penetration Capability 

7.1.1 State -of- the -Art Capability 

7.1.2 Near Term Capability 

7.2 Chip Removal 

7.3 Hole Stabilization 

7.4 Guidance 

7.4.1 State -of- the -Art 

7.4.2 Near Term Capability 
Planning and Estimating Horizontal Drilling 

Selecting a Drilling Technique 

Horizontal Drilling as a Development Program 

Costing Model 
Equipment Manufacturers and Contractors 
Address Listing 
Grouting 



Page 

6- 118 
6- 118 
6- 119 
6- 119 
6- 133 
6- 134 
6- 134 
6- 138 
6- 145 

6- 145 

6- 147 

7-1 

7-1 

7-1 

7-4 

7-7 

7-7 

7-7 

7-7 

7-11 

8-1 

8-1 

8-1 

8-3 

A-l 

B-l 

C-l 



Glossary of Terms 

References 

Bibliography 



iv 



LIST OF ILLUSTRATIONS 



Figure Page 

2.1 State -of- the -Art Horizontal Penetration Capability 2-6 

3.1 Drilling Method Selection Process 3-2 

5.1 Generalized Horizontal Drilling Procedure 5-6 

5.2 Horizontal Rock Penetration from Horizontal Boring 5-10 
Technology: A State -of- the -Art Study , Paone, et. al. , 
September 1968 5 

6.1 Horizontal Diamond Wireline Core Drilling 6-3 

6.2 Diamond Drilling Rig (Courtesy, Boyles Diamond 6-6 
Drilling Equipment) 

6.3 NQ Overshot Assembly (Courtesy, Acker Drill 6-9 
Company, Inc.) 

6.4 NQ Wireline Core Barrel (Courtesy,. Acker Drill 6-10 
Company, • Inc.) 

6.5 Diamond Core Bit (Courtesy, Christensen Diamond 6-11 
Products) 

6.6 Coring Bit Thrust Requirements 6-13 

6.7 Coring Bit Torque Requirements 6-14 

6.8 Ratio of Thrust Friction to Torque Friction as a 6-17 
Function of Hole Size 

6.9 Horizontal Diamond Wireline Coring Penetration 6- 19 
C apability 

6.10 Vertical Rotary Drilling 6-21 

6.11 Horizontal Rotary Drilling 6-22 

6.12 Milled- Tooth Rolling Cutter Bit (Courtesy, Hughes 6-28 
Tool Co.) 

6.13 Insert Rolling Cutter Bit (Courtesy, Hughes Tool 6-29 
Co.) 

6.14 Rolling Cutter Bit Thrust Requirements 6-31 

6.15 Rolling Cutter Bit Torque Requirements 6-32 

6.16 Horizontal Rotary Drilling Penetration Capability 6-34 

6.17 Horizontal Down- Hole Percussive Drilling 6-36 

6.18 Down-Hole Percussion Drill 6-38 

6.19 Percussion Bit 6-41 

6.20 Horizontal Down-Hole Percussive Drilling Penetration 6-42 
Capability 



LIST OF ILLUSTRATIONS (Continued) 

Figure Page 

6.21 The Dyna-Drill Positive Displacement Down- Hole 6-45 
Motor (Courtesy, Dyna-Drill Co.) 

6.22 Horizontal Down-Hole Motor Drilling Penetration 6-47 
C apability 

6.23 Continuous Core Drilling (Courtesy, Drilco Industrial 6-49 
Operations) 

6.24 Continuous Cuttings Sampling (Courtesy, Drilco 6-50 
Industrial Operations) 

6.25 Flushing Fluid Flow Rate Versus Hole Diameter 6-55 
for Various Drill Rod Sizes 

6.26 Pressure Drop as a Function of Hole Size, Drill 6-56 
Rod Size, and Hole Length for Hydraulic . and 

Pneumatic Chip Removal 

6.27 Installation Procedure for Horizontal Drainage Screens 6-60 
(Courtesy, Tigre Tierra, Inc.) 

6.28 Formation Drillability Theory of Hole Deviation 6-65 

6.29 Drill Collar Moment in Drilling Dipping Formations 6-65 

6.30 Tendency of Bit to Drill Perpendicular to a 6-66 
Moderately Inclined Bedding Plane 

6.31 Whipstock Effect Caused by Change in Formation 6-66 
Hardness in Steeply Dipping Beds 

6.32 Tendency/ of Bit to Follow Bedding Planes Intercepted 6-68 
at a High Angle 

6.33 Guide for Selecting Non-Magnetic Drill Collars 6-71 

6.34 Survey Coordinate Systems 6-73 

6.35 Drill String Elements 6-76 

6.36 Stiff Bottom - Hole Assemblies (Courtesy, Drilco 6-77 
Division of Smith International, Inc.) 

6.37 Stiff Bottom - Hole Assemblies (Continued) 6-78 

6.38 Stiff Bottom - Hole Assemblies (Continued) 6-79 
6.39a Fulcrum Effect on Bit Forces 6-82 
6.39b Climbing Configuration 6-82 
6.39c Falling Configuration 6-82 

6.40 Deviating a Hole with a Whipstock 6-85 

6.41 Typical Magnetic Multi-Shot Instrument 6-88 



LIST OF ILLUSTRATIONS (Continued) 



Figui 



6.42 Typical Directional Instrument Assembly 

6.43 Gyroscopic Survey System 

6.44 Survey Steering Tool 

6.45 Whipstocks: (a) None ire ulating Whipstock (b) Cross 
Section of Circulating Whipstock 

6.46 Knuckle Joint 

6.47 Down-Hole Turbine Motor 

6.48 Bent Housing and Bent Sub Dyna-Drill Assemblies 
(Courtesy, Dyna-Drill Co.) 

6.49 0-90° Compass Angle Picture 

6.50 Sperry-Sun Calibration Accuracy Determination 

6.51 0-130° (High Angle) Compass Angle Picture 

6.52 Steering Error vs. Length 

6.53 State -of- the -Art Guidance Capabilities 

6.54 Primary Fishing Tools (Courtesy, Houston 
Engineers, Inc.) 

6.54 Primary Fishing Tools - Continued (Courtesy, 

Hendershot Tool Co.) 

6.54 Primary Fishing Tools - Continued (Courtesy, Bowen 
Tools, Inc.) 

6.55 Accessory Fishing Tools 

6.55 Accessory Fishing Tools - Continued (Courtesy, 

Homco International, Inc.) 

6.55 Accessory Fishing Tools - Continued (Courtesy, 

The Dial- Log Co.) 

6.55 Accessory Fishing Tools - Continued (Courtesy, 

Tri-State Oil Tool Industries, Inc.) 

6.55 Accessory Fishing Tools - Continued (Courtesy, 
Baa sh- Ross Div., Joy Mfg. Co.) 

6.56 Split Tube Core Barrels (Courtesy, Christensen 
Diamond Products) 

6.57 Orienting Core Barrel and Scribed Core Sample 
(Courtesy, Christensen Diamond Products) 

6.58 Core Goniometer and Thin Core Sections 



LIST OF ILLUSTRATIONS (Continued) 



Figure 



Page 



6.59 Soil Sampling Devices (Courtesy, Soiltest Inc.) 6-143 

6.60 Hunt Sidewall Coring Tool (Courtesy, Hunt Oil 6-146 
Tool Co.) 

6.61 Lynes Pressure Sentry (Courtesy, Lynes, Inc.) 6-149 

6.62 Ground Water Pressure Measurement Using Lynes 6-150 
Sentry 

6.63 Permeability Measurement Using Lynes Pressure 6- 151 
Sentry 

7.1 State -of- the -Art Horizontal Penetration Capability 7-2 

7.2 Projected Horizontal Penetration Capability of 7-8 
Available Adaptable (Near Term) Equipment and 
Procedures 

7.3 State -of- the -Art and Projected Near Term Guidance 7-10 
C apability 

8.1 Drilling Method Selection Process 8-2 

C. 1 Effect of Drilling Fluid on Grouting Activities C-2 

C.2 Average Cost per Foot for Hole Lengths of C-17 

1, 000 Through 5, 000 Feet 



viii 



LIST OF TABLES 



Table Page 



1.1 Long Horizontal Drilling Time and Cost Estimates 1-5 

for Average Geology. 

2.1 Representative Horizontal Drilling 2-2, 

2-3 

2.2 Long Horizontal Drilling Time and Cost Estimates 2-8 
for Average Geology 

6.1 General Equipment and Materials List for Diamond 6-5 
Wireline Core Drilling 

6.2 Diamond Core Drilling Hole Dimensions . 6-7 

6.3 Diamond Drilling Rig Specifications 6-15 

6.4 Drill Rod Data 6-18 

6.5 General Equipment and Materials List for Horizontal 6-24 
Rotary Drilling 

6.6 Rotary Drilling Rig Specifications 6-26 

6.7 Approximate Air Consumption for Down- Hole 6-39 
Percussion Drills (Does not include chip removal 
requirements) 

6.8 Long Underground Horizontal Exploratory Drill 6-113 
Holes and Target Results 

6.9 Maximum and Minimum Expected Values for 6-116 
Surveying and Steering Parameters 

6. 10 Wineline Core Barrel Sizes 6-13 5 

C. 1 Commercially Available Particulate and Chemical C-5 

Grouts 

C 2 Unconfined Compressive Strength of Grouts C-7 

C.3 Grout Cure Time C-7 

C.4 Grout Cure Time and Cost Estimate C-10 

C 5 Grout Quantity Estimates C-10 

C. 6 Summary of Time Estimates - For Hole Lengths of C-12 

1000, 2000, 3000, 4000, and 5000 Feet 

C.7 Cost Estimate for Hole Lengths of 1000, 2000, 3000, C-13 

4000, and 5000 Feet 



LIST OF TABLES (Coat. ) 

Table Page 

C.8 Cost Estimate for Hole Lengths of 1000, 2000, C-14 

3 000, 4000 and 5000 Feet 

C. 9 Cost Estimate for Hole Lengths of 1000, 2000, C-15 

3 000, 4000 and 5000 Feet 

C-10 Cost Estimate for Hole Lengths of 1000, 2000, C-16 

3 000, 4000 and 5000 Feet 



1 



1. Introduction 



1.1 Background 

Subsurface construction is the subject of increased interest in 
many sectors of our economy. Transportation planners would like to make 
greater use of the subsurface both to minimize the environmental impact of 
transportation systems and as a technique to reduce travel distances between 
points. Competition for space and noise considerations essentially demand 
that much needed urban- suburban mass transit systems be located under- 
ground. Large scale tunneling projects to overcome natural obstacles, such 
as the Seikan Railway Tunnel in Japan and the proposed tunnel under the 
English Channel ("Chunnel"), have contributed and will continue to con- 
tribute to the demand for improved subsurface construction techniques. 

Utility industries are also under increased pressure to 
locate lines and facilities underground due to environmental considerations. 
Further, the disruption caused by cut and cover techniques has become 
unacceptable in some situations (river crossings and urban environments) 
creating a requirement for underground construction to be conducted by 
tunneling techniques. 

The energy crisis has added to demands for underground 
construction and exploration techniques. In the coal mining industry, 
horizontal drilling is being used for methane drainage and relief of high 
pressure gas pockets. There is a strong push to use methane from 
coal beds to augment natural gas supplies. The Bureau of Mines 
estimates that, nationwide, coal seams less than 3,000 feet deep contain 
more pipeline quality gas than all of Alaska's present reserves. Ex- 

ploratory and production drilling in the petroleum field has been in- 
creasing as rapidly as the availability of equipment will allow. Under- 
ground facilities are being considered for insitu retorting of shale oil. 
In the atomic energy field, a shortage of underground radioactive waste 
storage facilities has caused the Atomic Energy Commission to require 
some atomic power plants to curtail electrical production. Leakage 
problems with existing storage facilities have lead to a program in 



1-1 



which precision horizontal and angled drilling is being used in implanting 
underground monitors at the facilities. 

At the present time, subsurface utilization in all areas is 
limited by high construction costs. A major element of these high costs 
is generated by the heavy financial and physical risks which derive from 
the uncertainty in predicting ground conditions at construction sites. 

This study focuses on the particular problem of subsurface 
investigation along proposed tunnel alignments but clearly the solution to 
this problem will be of benefit in all areas requiring the application of 
underground exploration and construction techniques. Horizontal pene- 
tration is recognized as the only alternative available, under many 
conditions, for generating continuous data along a tunnel alignment. 
Typically, this penetration would be achieved by excavating a pilot tunnel 
along the proposed tunnel line. However, pilot tunnel costs have esca- 
lated to the point where they presently range from $225 per foot for "easy 1 
conditions to $877 per foot for "difficult" conditions. Horizontal, reuse- 
able boreholes, explored with a combination of sensing techniques, have 
been suggested as an alternative method of horizontal penetration. 

1. 2 Purpose 

The purpose of this report is to serve as a guide to the 
highway or transportation engineer in evaluating subsurface investigation 
techniques. In particular, this document provides the information needed 
to evaluate guided horizontal drilling as an alternative to pilot tunneling 
for achieving horizontal penetration. 

In investigating the geology of a proposed tunnel site, the 
engineer will generally use the following techniques: 

1. ) Evaluate local knowledge of the geology based 

on nearby mines, tunnels, and other previous 
subsurface construction. 



1-2 



2. ) Examine geological maps, aerial photographs, 

and possibly, radar or infrared scanning imagery. 

3. ) Extrapolate conditions on the basis of an 

examination of the surface geology. 

4. ) Drill vertical and inclined core holes. 

If the tunnel alignment is close to the ground surface and 
the surface is accessible, discontinuous, direct penetration data may be 
obtained by widely- spaced, vertical or inclined core holes. If the tunnel 
is located under a high mountain or if access to the ground surface is 
difficult or impossible, horizontal penetration may be considered as a 
means of obtaining continuous data along the tunnel alignment. This 
horizontal penetration can be achieved by excavating a pilot tunnel or 
by horizontal boring techniques. 

Pilot tunnels have shortcomings which suggest that more 
attention should be paid to alternative horizontal penetration techniques. 
A few of these shortcomings include: 

1. ) High Cost 

2. ) Long excavation time. 

3. ) Danger to the personnel involved. 

A subsurface investigation system employing horizontal 
drilling and a combination of sensing techniques is one alternative to 
pilot tunneling. The purpose of this document is to provide the informa- 
tion necessary to evaluate horizontal drilling as a technique for hori- 
zontal penetration. No indirect sensing techniques are considered. 
However, an FHWA contract now in progress is developing a sensing 



1-3 



system to be used in horizontal boreholes for pre- excavation investiga- 
tion of tunnel sites. The sensing device developed from this program 
will constitute one of the components of an information gathering system 
using horizontal drilling as a penetration technique. 

1. 3 Summary of Results 

The results of this study indicate that there are four 
candidate techniques for drilling long-range horizontal boreholes in rock 
and gouge. These include: 

(1) Diamond wireline core drilling. 

(2) Rotary drilling. 

(3) Down- hole motor drilling. 

(4) Down-hole percussive drilling. 

The estimated penetration capabilities and costs of these 
techniques are listed in Table 1.1. Diamond wireline core drilling is 
far and away the most developed horizontal rock drilling technique. 
With this technique, the prospective horizontal drilling customer has 
the choice of purchasing the equipment himself to perform the work 
or hiring a contractor. There are no contractors who make a practice 
of horizontal drilling in rock with the other listed techniques. Of these 
techniques, down-hole motor drilling would probably require the least 
amount of development effort in a horizontal drilling program and down- 
hole percussive drilling the most. 

With available drill guidance techniques, hole deviation 
can be controlled to about + 11 ft (3.3 m) per 1000 ft (305 m) drilled, 
"best case", and about + 44 ft (13.4 m) deviation per 1000 ft (305 m), 
"worst case". Performance will vary within this range, depending 
more upon the care employed in using the available equipment, than the 
equipment itself. 



1-4 



' — 
















7T 
















<3) 
















■£ A 
















V +•> 
















sa> 
















w a) 
















*jj 
















o 
















fS | 
















o 




co 


r~ 




CO 




o 




oo 


in 




o^ 




££ 


CM 




<\] 


F- < 




cq 


















0) .w 
















& B 


1—1 




sO 


oo 




o 




«j 


vD 




00 


•* 




oo 




CO <i 
















^ 
U rt 


m- 




«e- 


■w- 




■W- 




11 








(sT 














m 






_ 


^^ 


„^ 


■—1 


i 




r— 1 


vO 


nJ 


o 


vO 


r- ^ 


CO 




r- 


r- 


• rt to 

Q a> 


vO 


f- 


— < in 


o 




i— i 


— ' 






— ' o 










xi 






co 










0) u 


NO 


00 


in £i 






in 




7l CS 


CO 


o 


r~ 


sO 




r~ 




O -H 






. CM 


I 








X 


c<i 


CJ 


v£ ^H 


^ 




sO* 


co 


.d 
















+• 


^F* 


o* 


^ 


^^ 




o" 


o 


OO 


(VJ 


CM 


CO 


m 




CO 


■— 1 


in 


PJ 


in 


o 




CM 


sO 


£3 


^ 


r-H 


CO 




i. 


— 


r-J <U 


o 


o 


o o 


o 




O 


o 


o 


o 


o 


o 




O 


o 


o 


o 


o 


o 




O 


o 


ffi 


in 


•* 


m 






-tf 


CO 












00 
















a 








<D 








•H 








fl 








5=1 










00 

i 

U 

Q 

<D 
U 
O 


00 

a 


i-H 


Q 
> 


1—1 


00 


•l-l 

J 

o 
H 


o 

a 
2 


Q 

$ 
o 


o 

a 

o 


to 
to 



o 
u 



o 

a 




Q 

u 
o 

+» 

o 

2 




S 


O 


tf 


Q 


Ph 


Q 



1-5 



Within the penetration and guidance limitations noted above, 
horizontal drilling offers a substantial cost saving over pilot tunneling 
as a means of achieving horizontal penetration. Furthermore, there 
is a considerable potential for extending the penetration capabilities of 
horizontal drilling and reducing hole deviation. These improvements 
are possible at a reduction in the time and cost required to drill a 
given distance. 

i 

1. 4 Report Format 

In evaluating horizontal penetration as a . subsurface 
investigation technique, the following steps are involved: 

(1) An assessment of the capabilities and 
economics of available penetration techniques. 

(2) A value analysis of the information gathering 
potential of penetration techniques and associ- 
ated sensing techniques. 

(3) Selection of the most cost effective information 
gathering system. 

(4) Detailed planning of the proposed horizontal 
penetration. 

This document is written as an aid in tasks 1 and 4 of 
the decision- making process. To this end, the report is divided into 
three distinct sections. Chapters 2-4 of Volume I constitute an Execu- 
tive Summary of the state-of-the-art of long horizontal drilling. This 
section provides a comprehensive but succinct assessment of available 
horizontal drilling techniques. Chapters on Planning Considerations 
and Management Considerations are included to outline the qualitative 
factors which should be considered in evaluating horizontal drilling. 



1-6 



The remainder of the document serves as a reference 
for the detailed planning of a long horizontal drilling program. Chap- 
ters 5-8 comprise the Technical Discussion section of the report. 
These chapters include detailed discussion of all aspects of horizontal 
drilling. Volume II, the third section of the report, presents a 
mathematical model which can be used to estimate time and cost 
requirements for horizontal drilling. 

Procedures for performing a value analysis of information 

gathering systems are presented in a previous FHWA report on Subsur- 

4 
face Investigation Planning. This document is an essential reference 

in any decision involving subsurface investigation techniques. 



1-7 



Part I - Executive Summary 

2. State -of -the -Art Horizontal Drilling Capability 

The state-of-the-art of horizontal drilling is defined in terms of 
the capabilities of available production hardware and techniques which 
have been proven in horizontal drilling applications. Custom equipment, 
experimental equipment and the procedures associated with its use, and 
production equipment which has not been applied to horizontal drilling 
are not considered state-of-the-art. However, custom, experimental, 
and conceptual equipment and procedures are considered in evaluating 
near term horizontal drilling potential as is the modification of available 
production equipment to horizontal drilling. 

2. 1 Horizontal Drilling History 

A listing of representative horizontal drilling is provided 
in Table 2.1. The discussion which follows refers to that drilling which 
is of particular significance in terms of establishing state-of-the-art 
capabilities for drilling long horizontal holes in rock. 

The longest horizontal hole which has been drilled appears 
to be a 5,300 ft (1615 m), 6-3/4 inch (172 mm) diameter hole which was 
drilled about 1971-1972 on the Seikan Tunnel Project in Japan. This 
hole was drilled with an FS-400 Horizontal Boring Machine manufactured 
by Koken Boring Machine Co., Ltd. of Tokyo, Japan. A three cone 
rotary bit was used for drilling, a Dyna-Drill was used for hole direc- 
tion changes, and a Sperry-Sun magnetic multishot survey instrument 
was used to survey the hole. 

Diamond coring procedures have been utilized in all other 
horizontal drilling work beyond 2, 000 ft. (610 m) in length. Longyear 
Company of Minneapolis, Minnesota and Longyear subsidiaries in Canada 



2-1 











a 






















Ji 


■v 
















o 


H 


nl 


to a 


2 




3 

H 




H 






c 
H 


a 


c g 
It 


< 


1.1 


3 




d5 a 




J3 
IS 






ll 




3 A 

co >-> 



CO 


u u 


i 




co " 




$8, 






(0 -. 





























f; 


V 


3 


IM C 




^ 


41 




^ 


c 




















































Q 


2 


O U 

HO. 


H 


z£ 




Z 


i- 

Hfc 


2 


- 


Hft 








-J 












^ 












•d « 


fa 


« u 








■§ 
















u u 
















U 




DfijO 

3 "> 


o o 


'£< 

3 t 


o d 




0) 




fa o g 

• ■2 2 


I 


a. 


o 




Q 2 


^2 


-o C 


5 - 






2 


§£f 


^<n^ 


a 


o 

U 


•g 




■g M 


«i^ « 


^U 


t-3 




{j 


M • 


> .3 s 


c 


1 












O fa 






o. « 3 








y 




UJl 


a js 


OP 




M 


CO&,< 


O In CQ 


H 


H 




~ 
























6 § 


o 
























5j 










* 
















































o 










-j 


*•— . X o 


~~ 




p 




i 


~ 


1 


i 


i 


i 




•; o c o 


o 




















o 


Jo ** 


o 










1 












^ 
















^ 






























■v 




■v 


c 










£ g. 

o E 


i.0 


, 




O 


ioQ 


£ 


(S 


p 


N^ 






fa o 
H U 


&f 


















£ 




■a 
o 


•O ao 




30 


















^ o 


2 5 






















»i 


E . 




« 'fa ^ 


E 
















5 c 


2- S 
Q 'fa jS 




a 
3 


1 




o 
U 


o 2! 


U 


CO 
o N 
° J 


* 


ii 


— 




ifj 


5 


■° * 


■o £ 


■o J| 


■O m 


T3 W 


c 


*o „, 


«j i to 


C 


H o '• 





« 5 




c K 
i. 
E " 




C J 
£ » 


0^ 

£ g 


1 




S.^, 

■So 3 


Q 


„ « CIO 

2»J» 


U 


CO 


.2 § 


.2 o 


.2 § 


.2 o 


.2 o 







5 "i >. 

o " o 


g, 


4) o O 


'2 


(fain 


Q J 


QJ 


Q J 


DJ 


OH 


Cfa 


5 io 


Qtn-i 


a 


« 
















































5 




£ 


£ 


o 
in 


£ 






£ 












3 


3 


















2 


I 


11 


3"8 

25 


> 


Si 


co 


o 


2 = 


o o 



(O 


CO 


i 
























3 


£ 


o 


o 


















"2 


IX 


■a 


-o 


_ 


o 












_ 
















































E » 






































































s-s 


•c 


■^ 


> 


^ 


fa 


1 


N 


<*> 


^, 


So 


m 


~J5 


s 


o 


o 


s 


~ 


— 


— 


~ 


jj 


? 


— 














o 




o 


































































o 


o 


o 


o 


o 






a & 


o 




o 


















2 




















It 


•* 










































































(n 


















o- 








~ 


~ 


*■" 


~ 


" 


~ 


~ 




~~ 


~ 



M CQ 

d a) 



2-2 













c - 















































i" 








5 








c 


B 








4 








•- 


H 








h 








It 


4 


Jl 








2 
O 


Jo 
So 




2 
o 














































ai 


















































Q 




HI 


h£ 


— 


2 


2 


o 




c 








c r 


1 


c 






O 




c 


M 


c 


< 


o a 


o 


5 







2 


a 

E ■ 





c 


"« . 


< 


&% 


« 




•3 .y 


■3.S 


* a 


s s 


"1% 


-2< 


= .s 


| 




c t 


o i 


c u 


ll 




*<* 


>. 


U 




Uin 


in in 


U. 03 


Uoi 


UH o 


->«: 


COOU 








— c 


































o 


"1 J| 








o 




■ 




£ 


~£ « 








C2- 








o 


o 5 








o 








o 


o .e £ 








o 




o 




° 


o Ji o 








o 






^ 






- .- 




o 




S 


-o 


3 5 




, 


a £ 3 
in Z u 

>-.S£° 


■a c oo 

ll'a 


11 1 is i^ 

3 " «-3 2 c 


. 


in « ; c s i< 


o 


&Q 






inQCUQ 


5 S " 

2hS 


UHmHQID 


o 
Z 


c 3 « o >.£ 
O in Q< Q I in 
















^ 






o 
o 










^; 


> 




E 
a 

0" 

U 
■o 
J 


U3 




W 

.5 ■ 

£ 

III 

.2 § S 


2 M 

»H j 
rt .2 


2 rt 

*-> 

tt a 

o a 




u 

c S 

S. 

iff 

.3 o 


i2 

O ffltt! 
g.0 


a 

U TP 

l. e 

V A 

o "3 

* £. 

o S? 


fi " 


1 


a 


DS«H 


Ctfffl 


D J 


a! in J 


a .5 


a ixa 


^ 


















a 




£ 

3 






E 


o 
U 


£ 
a 




U 


2 


I 


=3 "2 


1 




U 


s5 


1 


"0 u 

Si 


I 


0) 




































E 






o 












sf 


&■ 


o 


£ 


<? 




? 




a 




















§5 

2 -c 


~°. 


s 


« 


I 


c^ 


"i 


2 


— 


Q c 






































































= ? 


a 


S 


o 


£ 


c. 


s 


2 


* 






















o 
















s| 




s 


-' 


o 


1 


o 


3 


o 












































* 












Ik 


















""" 


w 


" 


~ 


"" 


w 


w 


~ 



2-3 



and South Africa have drilled holes out to about 4,000 ft. (1219 m) 
using diamond wireline coring techniques. This work has been performed 
in medium and hard rocks. The South African subsidiary of Longyear 
(Boart Drilling, Ltd. ) anticipates that they will eventually drill horizontal 
holes to 5,000 feet (1524 m) on work in progress as of May 1975. Hole 
diameter on this work is 2.3 6 inches (60 mm) (BQ size). 

Boyles Brothers Drilling Co. of Salt Lake City, Utah has 
used similar equipment to drill horizontal holes to 3, 000 feet (914 m) in 
length in medium and hard rock. 

Again using similar equipment, the Atomic Energy Com- 
mission (AEC) has drilled horizontal holes as long as 2,690 feet (1125 m) 
in continuing work at the AEC test site near Mercury, Nevada. These 
holes are about 3 inches (76 mm) in diameter and are being drilled in 
very soft materials. The contractor on this work is Reynolds Electrical 
and Engineering Co. of Las Vegas, Nevada. 

Sprague and Henwood, Inc. of Scranton, Pennsylvania 
drilled a 3 inch (76 mm) (NX size), 1,980 foot (604 m) horizontal hole 
in 1954 using diamond coring techniques. This work was performed for 
the Pennsylvania Turnpike Commission and the material drilled was 
medium and hard rock. 

Jacobs Associates of San Francisco, California developed 
a technique for drilling horizontal holes using a pneumatic downhole per- 
cussion drill in 1972. This technique was used to drill 4 inch (102 mm) 
holes in medium and hard rock. The longest hole drilled was 864 feet 
(263 m). The Jacobs work also included the development of drill rod 
handling equipment which enabled 1,000 ft (305 m) sections of drill pipe 
to be inserted and withdrawn at up to 200 feet (61 m) per minute. 



2-4 



2.2 Assessment of State -of -the -Art Horizontal Drilling Capability 

If we define the state-of-the-art of long horizontal drilling 
in terms of the capabilities of available production hardware and tech- 
niques which have been proven in horizontal drilling applications, the 
state-of-the-art can be diagramed as in Figure 2.1. There would be 
some overlap and the numbers have been rounded off but this figure 
represents a realistic graphic summary. 

In terms of accuracy, the range of hole deviation which 
can be expected is about +11 -44 ft (3.3 - 13.4 m) horizontally per 
1000 ft (305 m) of length and + 8 - 19 ft (2.4 - 5. 8 m) vertically per 
1000 ft (305 m) of length. 

Grouting has been proven capable of handling most 

hole stabilization problems given that one is willing to spend the time 

and effort. One 2,600 foot (792 m) hole drilled for the Seikan Tunnel 

job was grouted 61 times, with the number of grouting shifts being twice 

5 
the number of drilling shifts. However, the material drilled in this 

work was soft and broken. In diamond coring work performed in medium 

and hard rocks, hole stability has not been noted as a significant problem. 

The cost model of Volume II presents the following tech- 
niques as state-of-the-art candidates for horizontal drilling: 

(1) Diamond wireline core drilling. 

( 2 ) Rotary drilling. 

(3) Down-hole motor drilling. 

(4) Down-hole percussive drilling. 

The cost model has been used to project costs for all four 
techniques out to 5,000 feet (1524 m). However, diamond wireline core 
drilling and rotary drilling are the only techniques which can be con- 
sidered to meet the definition of state-of-the-art for the longer distances. 



2-5 



(s-isiaurrj^Tj^;) 



o 


1 1 1 


1 1 


1 




o 










in 








> 


— 


i-H 


CO 

a 


/ 




/ 

4) 




O 


•iH 






•H C 


> 


o 


— o 






££ 




o 


nJ 


1 






T— < 


2 
C! 
O 

pq 

OD 


/ 60 










CO 


/ -S 








- 




CO 


/ *"" ' 










o 
o 
in 


o 
H 
U 

O 


/ »H 

/ H 

/ p 
/ ^ 

/ o 


00 

Q 










I 


/ ^ 




0) a) 










/ 




3£ 










/ 




















/ 




Si ° 










. 1 1 1 1 


1 / 1 1 










1 



a 



<-> 




nJ 


o 




U 


o 






m 






ft 
CD 

a 


O 




V 


o 




Ph 


o 






<* 




,— ( 






ft) 










9) 


a 




<u 







M-I 


N 




A 


h 


o 
o 
o 


W) 


ffi 


m 




ft 

< 






<u 




o 


,d 




ffi 


«*H 


o 







o 




1 


o 




0) 


r\j 







(saqout) Js^stu^Ta 3TOH 



2-6 



Of these, diamond wireline core drilling is far and away the most 
developed technique. Information on the cost and performance capabilities 
of the Koken FS-400 horizontal rotary drilling machine has been limited. 
It has been assumed that this machine would cost $100,000 for the purpose 
of exercising the rotary drilling cost model. Table 2. 2 presents cost 
and time figures for the candidate drilling techniques for an "average" 
geological model. (11% soft rock, 59% medium rock, 3 0% hard rock.) 
For the non-coring techniques, a sample core is taken at 60 ft. (18.3 m) 
intervals. 

Contractor estimates for a 5,000 foot (1524 m) hole drilled 
with diamond wireline coring equipment (the only technique for which con- 
tractor estimates are available) ranged from $50 to $100 per foot ($164 - 
$329 per meter). However, the concensus of contractors' opinions was 
that they would only undertake long horizontal drilling under a "time and 
materials" contractual arrangement. 

It is clear that horizontal drilling is a substantially 
cheaper method of achieving penetrations along tunnel alignments than 
pilot tunneling. However, the state-of-the-art penetration capability of 
horizontal drilling is realistically about 5,000 feet (1524 m). Maximum 
hole diameter is limited to less than 11 inches (279 mm) for distances 
greater than 1000 feet (305 m). 

2. 3 Limiting Factors in Horizontal Drilling 

In the broad sense, the most significant factor limiting the 
state-of-the-art of long horizontal drilling has been a lack of demand. 
It is frequently stated that long horizontal drilling is little used because 
it is expensive. It is much more accurate to conclude that horizontal 
drilling is expensive because the demand for it has not been sufficient to 
support the development of effective, economical techniques. In all prob- 
ability, less than 10 horizontal holes have been drilled to 4000 ft (1219 m) 
and beyond. Contrast this with the petroleum drilling industry where an 



2-7 

















in 












CM 












m 


o 


CM 










f — . 


00 


i 


i 




o 


i— i 


m 








o 


CO r-l 


CM xO 








o 


NO 


00 








in 




















"u 


© 










O 


CM 
<M 










+■> 


Tf 


CO 


CM 




4) 




1—1 i—i 


s {3 


2 M 






sO >— 


o — 


O -^ 


i 


— S 


O 

o 


i-< 
CM CO 


r- 


oo 

.-H O 




fn 


© 


in 


c- 


00 




o> & 


<tf 
































I . 


_^ 












in 


^_, 


^ 


^ 




-i-i co 

CU 


Qs 


00 


CO 


co 






^2 <-> 


00 pj 






**4 


o 


Tf -_■ 


CO =-i- 


o ™ 


i 


.m. 


o 


CO 


o 


i-H 




«r m 


o 

CO 


-h m 


r-H 00 


.-1 O 




4* h 


t 


v£> 


00 




5 o 






















co - 












Q oT 


o 


^^ 


^^ 


^ 






in 


r- 


co 




a 


t*- 


CM 


o^ 


^ 










CM 




•rt 




CM -^ 


"tf _ 


c>™ 


i 


H 


o 




in 


o 






o 


t> 00 


m o 


in -tf 






o 

(M 


CO 


sO 


r- 




_ 












in 












o 


in 


o 


o 


t>- 




co 


CM 


CO 


co 


m 








_^. •—* 


CM 


.. i-H 






in — 


■<t ^ 


CM — * 


r- -^ 




o 


t>- 


CM 


m 






o 


CM CM 


cm m 


CM o 


CM 00 




o 


CO 


in 


r- 


^ 




■"• 










•— i 










hn rt 




00 


00 


00 


terv 
(m) 


o 
o 


o 


o 


o 


U5« 


PH 


v£> 


xO 


vO 


& 

■H \? 












fv? 


CM 






r- 


t> 












Q S 


Co 


" ' 


' ' 


CM 

m 


<u i. 


r- 


m 


in 
r- 


i— i 


I.S 


co 


vO 


vO 


sO 


0) 








0) 


3 








> 


60 a 1 

Pi "3 


T3 0> 

gu 


u 
ct) 


O © 


•H 

CO 

co 
1 a 


QH 





O O 0) 



2-8 



estimated 3.4 billion dollars were spent in 1974 to drill 30,000 wells 
averaging 5,133 feet (1565 m) in depth. Any technique as little used 
as horizontal drilling is likely to be expensive, even if the procedures 
involved are quite trivial. 



However, the assumption is made that the demand for long 
horizontal drilling will increase substantially. Some of the factors which 
support this assumption are discussed in Section 1. 1. 

In a more specific vein, the factors which limit the 
application of horizontal drilling can be broken down in terms of: 

1. ) Penetration capability. 

2. ) Hole guidance accuracy. 

3. ) Economics. 

Factors which fall into the first category include the 
torque and thrust capabilities of existing surface equipment and the 
ability to transmit thrust and torque to the drilling bit. Only one piece 
of equipment has been designed to perform long horizontal rotary 
drilling and it is questionable whether this piece of equipment (Koken 
FS-400) is available in this country. The efficiency with which thrust 
and torque can be transmitted to the drilling bit are limited by drill 
pipe friction, a problem which is exacerbated by the buckling of the 
drill pipe. Downhole motors have not yet proven to be an economical 
solution to this problem in horizontal drilling. 

Hole guidance accuracy is limited by the capabilities of 
available survey equipment and steering tools. At the present time 
there are no survey tools available which can stay with the drill bit 
while drilling horizontal holes and there are no devices available which 
allow the drill to be steered remotely from the surface. 



2-9 



Among the many factors which affect the economics of 
horizontal drilling are the excessive time required for guidance oper- 
ations, drill rod handling, and, in core drilling, core retrieval oper- 
ations. 

There are, of course, other factors which limit horizontal 
drilling applications, but the above factors are particularly significant. 
Fortunately, equipment will soon be available to eliminate or reduce the 
effect of some factors. In some cases, equipment now used in other 
applications can be adapted for horizontal drilling or, if the demand is 
sufficient, experimental equipment can be made commercially available. 
Finally, and again if demand is sufficient, new equipment may be designed. 

2.4 Extending Horizontal Drilling Capabilities 

Raise boring machines have thrust and torque specifications 
which make them well suited for horizontal rotary drilling. With some 
modifications, these machines could function as effective horizontal 
rotary drilling machines. 

Blast hole drilling rigs can be repackaged to function as 
horizontal drilling rigs. Schramm, Inc. of West Chester, Pa. has 
packaged standard blast hole drilling components into a configuration 
suitable for horizontal drilling. This approach could be followed with 
the equipment available from most blast hole drill manufacturers. 

Drill pipe stabilizers which remain stationary while allowing 
the drill pipe to turn are used in petroleum drilling. This type of 
stabilizer could be adapted to rotary drilling as a means of controlling 
drill rod buckling while acting as a bearing between the drill pipe and 
hole. Stabilizers can be designed with an axial degree of freedom to 
reduce the effect of friction on thrust transmission. 



2-10 



Several manufacturers are pursuing programs to develop 
survey tools which can remain with the drill bit while drilling. Among 
the companies known to be financing development in this area are Shell 
Oil Co. , Exxon, Ramond Precision (TELECO), and Gearhart Owen. 
Telcom, Inc. of McLean, Virginia has developed a cableless telemetry 
system which has been employed for horizontal drilling in coal. Sperry- 
Sun and Scientific Drilling Controls, Inc. have real time, wireline survey 
tools which are used in directional drilling. These devices could be made 
available for horizontal drilling if demand were sufficient. 

Gyro tools are available to survey holes within + 1 foot 
(.31 m) per 1,000 feet (305 m) drilled. At the present time, these 
devices are better suited to surveying completed holes than to serving 
as a reference device in guided drilling. However, with some modifi- 
cation, they might be adapted to the latter function. 

A variable angle, remotely actuated steering tool is avail- 
able for vertical drilling. (Dyna-Flex, Dyna- Drill Division of Smith 
International, Inc.) This tool might be adapted to horizontal 'drilling. 
At least one other remote steering tool has been designed and success- 
fully operated on a proprietary horizontal drilling operation. 

Rod handling machines, such as the experimental device 
developed by Jacobs Associates, are readily adaptable to horizontal 
drilling procedure's and should result in substantial time and cost savings. 

Double tube, reverse circulation, continuous coring methods 
have been used for horizontal drilling on the Seikan Tunnel Project. 
(1,470 feet (448 m).) This technique is particularly promising as a 
means of speeding up core drilling. 

There is substantial potential for extending horizontal 
drilling capabilities in terms of increasing penetration capability and 
minimizing the deviation of the hole from the desired trajectory. 



2-11 



3. Planning Considerations 

3. 1 Background 

Geological investigation of proposed tunnel locations is 
generally conducted in three phases. The initial phase is a geological 
reconnaissance using available maps, aerial photography, and, on occasion, 
radar or infrared scanning imagery. The purpose of this reconnaissance 
is to obtain a gross indication of geologic conditions as a guide in sub- 
sequent investigations. The second phase of investigation is directed 
toward determining the feasibility of a particular location. During this 
phase alternative tunnel alignments are evaluated based on a comparison 
of geologic conditions in the area of the proposed tunnel. Procedures 
may include core drilling and /or geophysical studies, and collection 
and laboratory examination of rock samples. Once a tunnel site has 
been selected, the investigation enters the third phase. Studies conducted 
in this stage are intended to assist in the final design and estimation of 
the costs of the tunnel. It is assumed that the employment of long 
horizontal penetration procedures would commonly be confined to the 
third phase of the investigation. This assumption is based primarily 
on economic considerations. • Long horizontal penetration would undoubt- 
edly be the most costly element of the investigation and would therefore 
be employed where the information gained would be of maximum benefit 
i. e. along the actual tunnel alignment. 

3. 2 Site Selection 



Since long horizontal drilling would typically be employed 
after the tunnel route has been selected, the options available in selecting 
the drilling site will be limited. When there is a degree of flexibility 
in site selection, a primary consideration is to provide ample clearance 
behind the surface equipment so that drill rods can be handled in the 
maximum practical section length. The Jacobs Associates horizontal 
drilling program (item 18, Table 2. 1) employed techniques to handle 
drill rod in 1,000 foot (3 05 m) sections, substantially decreasing the 



3-1 



time required for drill rod handling. A second consideration in site 
selection is a ready supply of water for hole flushing. 

3. 3 Selection of a Drilling Method 

The options available in selecting a state-of-the-art technique 
for horizontal drilling are limited. Long horizontal drilling is not a 
common procedure. In all probability less than 10 horizontal holes 
have been drilled beyond 4,000 ft. (1,219 m) in length. The drilling 
techniques -which are defined as state-of-the-art include: 

1. ) Diamond wireline core drilling. 

2. ) Rotary drilling. 

3. ) Down-hole motor drilling. 

4. ) Down-hole percussive drilling. 

However, the level of development of these techniques for horizontal 
drilling applications varies markedly. 

Diamond wireline core drilling techniques have been 
employed most often in horizontal drilling. None the less, long 
horizontal drilling would represent an unusual job for any diamond 
drilling contractor. In terms of equipment capabilities, off-the-shelf 
diamond drilling rigs can be used for horizontal drilling, but the ratio 
of torque to thrust output for the rigs is not optimal for horizontal 
applications. 

Long horizontal rotary drilling with rolling cutter bits 
has been confined to the Seikan Tunnel work (items 1 an d 12, Table 2. 1) 
and de gasification holes in coal seams, (items 7, 15, and 17, Table 2.1) 
If rotary drilling is employed for a horizontal drilling project, a custom 
made surface rig will probably have to be employed. 

Application of the down-hole motor to long horizontal 
drilling has commonly been limited to drilling direction changes. 



3-2 



In this application the utility of the down-hole motor is severely com- 
promised by the lack of a "real time" survey tool for horizontal drilling. 
The use of the down- hole motor as the primary tool for advancing a 
horizontal hole is limited by a pricing strategy which is geared to an 
intermittent duty cycle. This pricing strategy is designed for the 
requirements of directional drilling in the petroleum field and its 
application to a straight hole drilling case causes the economics of 
down-hole motor drilling to become unattractive. 

The Jacobs Associates horizontal drilling project has 
been the only attempt to apply down- hole percussive drilling to long 
horizontal drilling, (item 18, Table 2. 1) This project did not address 
the problem of hole guidance. It is assumed that a down- hole motor 
could be employed to control the direction of a hole drilled with a down- 
hole percussive drill. 

Any long horizontal drilling project will involve some 
degree of the development effort. In general, the amount of develop- 
ment effort necessary will be at a minimum for a project employing 
diamond wireline core drilling and at a maximum when down-hole 
percussive drilling is employed. The development necessary when 
employing either of the other two drilling techniques will fall somewhere 
between these extremes. 

The above discussion of drilling method selection addresses 
the general problem of horizontal drilling in rock and gouge- 
For the specific case of horizontal drilling to investigate the geology 
along a proposed tunnel alignment, it is unlikely that any drilling technique, 
other than that of diamond wireline core drilling, will prove cost effective. 

3. 4 Drilling Costs 

The economics of various drilling techniques in specific 
horizontal applications can be evaluated using the model presented in 



3-3 



Volume II of this report. Table 2. 2 gives nominal estimates for 
planning purposes. 

3. 5 Site Preparation 

In addition to the specific procedures described for the 
various drilling techniques elsewhere in this report, a concrete pad 
will be required to ensure that the surface rig employed is properly- 
anchored. A second consideration is that the surface rig be aligned 
accurately in azimuth and elevation with the intended hole trajectory. 



3-4 



4. Management Considerations 

In theory, the prospective horizontal drilling customer has two 
choices in conducting a horizontal drilling program. He can purchase 
the required equipment, and hire the personnel required to perform the 
job or, he can utilize a contractor to perform the job. 

For any but the largest of horizontal drilling programs, the 
economics of the situation will favor contracting the work. The capital 
cost of the equipment, the scarcity of skilled personnel, and high 
utilization requirements are the major factors influencing the economics 
in favor of contracting. 

There are several contractors with some experience in long 
horizontal drilling with diamond core drilling equipment. (See Appendix A) 
However, it should be noted that horizontal drilling jobs are the ex- 
ception and they do not represent a substantial percentage of the con- 
tractors' work. Horizontal drilling by techniques other than diamond 
core drilling will probably still be contracted, but the customer will 
probably have to pay the capital cost for that equipment which is 
peculiar to the horizontal drilling job. As the overall demand for 
horizontal drilling increases, one would expect to see more con- 
tractors entering the field, and, with increased competition and higher 
equipment utilization, the economic factors should shift even more in 
favor of contracting the work. An increase in demand should also 
result in a greater willingness on the part of equipment manufacturers 
to invest time and money into development of new equipment and techniques. 

4. 1 Contracting Arrangements 

If a decision is made to contract a horizontal drilling pro- 
gram, there are three basic formats which the contract may assume. 
The advantages and disadvantages of each type of contract are discussed 
briefly in the following paragraphs. 



4-1 



4. 1. 1 Lump Sum Contracts 

The lumped sum contract calls for the completion 
of the hole at a fixed price or fixed price per foot. The specified 
price is to include all services and the contractor assumes all risks. 

Typically, this will be the most expensive type 
of contract. Due to a general lack of detailed knowledge about the 
conditions which will be encountered while drilling, the contractor will 
need to base his estimated costs on the worst possible situation. As 
the quantity and quality of information about hole conditions increases, 
the risk factor will decrease and this type of contract should become 
less expensive. However, since the purpose of the hole is to aid in 
assessing ground conditions, this type of contract will probably remain 
the most expensive. The- exception to this might be' in the case of 
multiple, closely spaced horizontal holes. 

The lump sum contract is seldom encountered 
in horizontal drilling. 

4. 1. 2 Mutual Risk Contract 



The mutual risk type of contract takes a form 
similar to the lump sura contract except that it provides certain escape 
clauses for the contractor. If no problems are encountered, the hole 
would be completed at a fixed cost or cost per foot. When problems 
arise, however, the escape clauses come into effect and the fixed cost 
per foot is supplemented by differing amounts depending on the problems 
encountered. Difficulties which might be covered by escape clauses 
could be exceptionally hard formations, unstable ground, excessive 
ground water, etc. 

This type of contract tends to be less expensive 
than the lump sum type and requires less accurate data about ground 



4-2 



conditions for realistic bidding. Mutual risk contracts are rare in 
horizontal drilling. 

4. 1. 3 Time and Materials Contracts 

In time and materials contracts, the contractor 
supplies all equipment, supplies, and manpower to perform the job, 
but assumes none of the risk. The total cost of the hole will depend 
heavily on exactly what difficulties, if any, are encountered. 

This type of contract tends to be the least 
expensive of the three types and is preferred by most contractors. 

4. 2 Contract Drilling Costs 

The cost of drilling horizontal holes is composed of four 
elements: 

1. ) Fixed costs, 

2. ) Variable costs, 

3. ) Indirect costs, and 

4. ) Risk factor. 

Each of these factors contributes to the total cost and the elements of 
each are discussed below. 

4. 2. 1 Fixed Costs 

Fixed costs include all expenses which will be 
incurred regardless of the progress of the operation. These costs 
would be composed of such items as depreciation, payroll, supplies, 
insurance, etc. These costs will normally be lumped together as a 
daily cost for rig operation. 



4-3 



4. 2. 2 Variable Costs 



Variable costs include those items which depend 
on the hole and drilling progress. Such items as drill rod, drilling 
fluid, grout, drill bits, etc. would be included under variable costs. 

The better the information about hole and drilling 
conditions, the better the estimate of variable costs will be. 

4. 2. 3 Indirect Costs 

Indirect costs are unique to the contractor. These 
costs will include the overhead and general and administrative costs 
and are generally expressed as a percentage of the direct costs. 

4. 2. 4 Risk Factor 

The risk factor used by a contractor is based on 
a number of considerations. Among these are such things as experience 
on comparable jobs, knowledge of the drilling conditions at the site, 
risks to be assumed, and the competitive situation. In a lump sum 
contract, the risk factor may comprise the largest single expense. 



4-4 



Part II - Technical Discussion 

5. Systems Analysis of Horizontal Drilling 

The goal of Part II of this report is to describe and evaluate 
procedures to (1) drill a horizontal hole which will meet specified 
requirements and (2) to gather information on the material being drilled, 
In the following sections, the specifications for the candidate procedures 
are detailed, a functional analysis of the problem is conducted, and 
candidate methods are selected. 

5. 1 Hole Specifications 

The horizontal drilling procedures described in this study 
should be capable of creating holes within the following specifications: 

(a) Hole Dimensions - Hole diameters of 2-24 
inches (51-610 mm) are to be considered. 
The maximum hole lengths obtainable with 
available techniques are evaluated within this 
range of diameters. 

(b) Accuracy - Guidance procedures are to be 
employed to minimize deviation of the hole 
from the desired trajectory. Deviation must 
be limited to + 30 ft (9.1 m) to ensure that 
the hole remains within the "area of interest" 
for investigation of the tunnel alignment. 

(c) Material Drilled - Candidate drilling methods 
must be capable of penetrating soft, medium, 
and hard rock and gouge. For the purpose 
of this study, rock hardness is defined in 



5-1 



terms of the unconstrained uniaxial compressive 
strength of the rock in the following manner: 

Soft < 8,000 psi (55.2 x 10 6 N /m 2 ) 

Medium 8, 000 - 22, 000 psi 

Hard > 22, 000 psi (151.7 x 10 6 N /m 2 ) 

Gouge is made up of thoroughly crushed and 
comminuted rock formed by the grinding 
action which occurs through the movement 
of the adjacent walls of a fault. Gouge 
formed in the presence of water . generally 
includes clay minerals and clay- size particles 
of other rock minerals. Gouge is found in 
large faults and minor subsidiary fractures. 
Normally gouge will deform plastically and 
under pressure it may squeeze into under- 
ground openings. For a more detailed 
discussion of gouge materials, see ref- 
erence 7. 

(d) Hole Life - The holes created by the pre- 

scribed procedures are required to remain 
open for up to one year. Metallic casing 
cannot be used to maintain the hole opening 
since it would interfere with some of the 
survey techniques which are being contem- 
plated for the completed hole. 

Procedures are evaluated for the following data gathering 
functions: 

(a) Core drilling and retrieval. 



5-2 



(b) Undisturbed sampling and retraction from 
gouge. 

(c) In situ measurement of water permeability and 
pressure. 

5.2 Functional Description 

5.2.1 Drilling the Hole 

Any drilling system must perform certain functions to 
accomplish the task of drilling a hole. These functions are required 
whether the hole is to be vertical, angled, or horizontal. While hole 
orientation does not alter the list of functions which make up the drilling 
task, it does change the variables which must be dealt with in per- 
forming the function. 



Drilling a hole along a specified trajectory in- 
volves four major functions: 

1. Material disengagement 

2. Transporting the disengaged material from the hole face 
(Chip removal) 

3. Ensuring that the hole remains open after the material 
disengagement device has passed. (Hole stabilization) 

4. Guiding the material disengagement device along the 
desired trajectory. (Guidance) 

In the following sections these functions are defined 
in more detail. 



5-3 



5.2.1.1 Material Disengagement 

Drilling systems are normally characterized 
in terms of the material disengagement technique which they employ (i. e., 
diamond drilling, percussive drilling, etc.). Material disengagement is 
the process of breaking down the material being penetrated. In conventional 
drilling techniques this involves breaking the material into a number of 
small pieces or chips. 

Regardless of the technique employed, 
material disengagement requires the expenditure of energy at the tool 
rock interface. The efficiency of drilling techniques is evaluated on the 
basis of the amount of energy expended relative to the volume of material 
removed. The energy expended by conventional techniques is a function 
of the strength of the material drilled and the size of the chips produced. 
Once a chip is created, it must be removed from the tool/rock interface 
or it will be further divided or ground. This regrinding wastes energy 
and reduces penetration rates. Therefore, the second major function 
required in a drilling operation is chip removal. 

5.2.1.2 Chip Removal 

Chip removal normally involves two steps, 
(1) flushing the chips from the tool/rock interface and (2) transporting 
the chips out of the hole. This function is common to all conventional 
rock drilling techniques. 

5.2.1.3 Hole Stabilization 

Hole stabilization involves keeping the hole 
open during the drilling operation and for a period of time after drilling 
is completed. 



5-4 



5.2.1.4 Guidance 

Guidance involves two distinct functions, 
defined as (1) survey and (2) steering. Survey procedures are used to 
establish the trajectory of an existing length of hole. Steering is in 
turn broken down into two functions, (a) maintaining the drilling assembly 
on the desired hole trajectory and (b) directing the drilling assembly to 
the desired trajectory when survey results indicate that a direction change 
is required. Drill string stabilizing procedures (not to be confused with 
hole stabilization procedures) are used to maintain a straight hole tra- 
jectory, deflection procedures are applied to make a discrete direction 
change, and variations of both procedures are used to drill a curved 
trajectory. 

5.2.2 Information Gathering 

Some geological information can be gathered by 
monitoring the drilling operation. Procedures for this are discussed 
in Section 5.3. Descriptions of the specific information gathering method- 
ologies prescribed in Section 5.1 are presented in Section 6. 

5.3 Procedures 

5.3.1 Drilling the Hole 

Figure 5.1 presents a flow diagram of a generalized 
procedure which applies to all conventional methods of drilling a hori- 
zontal hole. As indicated in the diagram, hole size, hole length, and 
the anticipated geology of the area to be drilled are primary considerations 
in selecting a drilling method. 

Having selected a drilling method and obtained the 
necessary equipment, the drilling operation begins with the setting up of 
the equipment. (Mobilization) An initial length of hole is drilled and cased 
to provide a stable reference for subsequent drilling. 



5-5 



Hole Diameter 




Hole Length 


1 r 








Geology 






H 






Selection of 
Drilling Method 




H 



1 Set Up and Collar! 



Drilling 



Coring 



Hole 
Stabilization 



Full 

Me. 



Guidance 



Rod . 

Handling 



I Survey j (Steering 



Fishing 



Equipment 
Maintenance 



Finished 
Hole 



Figure 5.1 - Generalized Horizontal Drilling Procedure 



5-6 



The drilling operation is broken down in terms of 
the activities involved. Drilling includes the functions of material dis- 
engagement and chip removal. These functions, along with hole stabili- 
zation and guidance, have been described in Section 5.2.1. Rod handling 
includes adding sections to the drill string as the hole advances and 
removing and reinserting the entire drill string to (1) change worn 
drilling bits, (2) change from a coring mode to a full hole mode, and 
vice versa, (3) correct hole stability problems, (4) change the drilling 
assembly as a part of steering operations, and (5) perform fishing 
activities. 



Fishing activities are required when a system failure 
occurs. Examples of such failures include, breaking the drill string 
("twist off" etc.) and "sticking" the drill string. (An inability to turn 
the drill string or move it in or out of the hole.) 

Equipment maintenance includes the preventative and 
corrective maintenance required for the equipment being employed. 

5.3.2 Information Gathering 

In Section 1. 3 the type of geological information 
available prior to undertaking a horizontal penetration program is dis- 
cussed. Geological mapping and surface investigations can determine 
rock types (relative percentages) and rock structure. Rock structure 
information can include attitude of beds in sedimentary formations, 
attitude of folds, attitude and dimension of faults, and attitude and 
frequency of fracture systems. This information base will be modified 
and added to by carefully monitoring the drilling operation. 

A qualitative evaluation of the strength of the 
formation being drilled can be obtained by monitoring the relationship 



5-7 



between the energy being applied to the drilling system (torque, thrust, 
etc. ) and the resultant penetration rate. 

The chips generated in the drilling operation can 
be retrieved and examined to determine what minerals the formation is 
made up of and to what degree, if any, alteration of the minerals has 
taken place. 

The coring mode of drilling accomplishes the dual 
program objectives of creating a hole and gathering information simul- 
taneously. 

A loss of circulation of the fluid being used to 
flush rock debris from the hole gives an indication of formation porosity. 

Hole stability problems or a lack of hole stability 
problems give an indication of the existence of formation weathering, fault 
zones, gouge zones, and a general indication of the competence of the 
formation. (Competent formations will support an opening without artificial 
support. ) 

The dip of the formation bedding planes and the 
presence of fault zones and other formation anolmalies can be inferred 
from their effect on hole trajectory. 

Ground water conditions can also be determined 
during drilling operations by observing water outflow from the hole. 

In summary, a great deal of geological information 
can be obtained by monitoring the drilling operation. Specific method- 
ologies for the data gathering activities listed in Section 5. 1 are described 
in Section 6. 



5-8 



5. 4 Drilling Methods 

5. 4. 1 Prior State-of-the-Art Studies 

There have been four reviews and evaluations 
of the state-of-the-art of horizontal since 1968. However, only one 
of these studies considered the use of horizontal drilling as a geological 
investigation tool in planning and estimating tunnel construction. 

Horizontal Boring Technology: A State-of-the-Art 
Study is a report on the state-of-the-art of horizontal boring technology 
for underground power transmission installations prepared by the Bureau 

o 

of Mines at the request of the Department of the Interior. This report 

has sections on rock penetrating methods and equipment and on borehole 
survey and guidance. Brief descriptions of capabilities, procedure, and 
available equipment are included. Figure 5. 2 is from this report. 
This figure presents a graphical evaluation of the horizontal rock pen- 
etration capabilities of various drilling methods. The report is dated 
September 1968. 

In 1972 Jacobs Associates of San Francisco 
conducted a program under the sponsorship of the Advanced Research 
Projects Agency on "Research In Long Hole Exploratory Drilling For 
Rapid Excavation Underground. " The objective of this program was to 
develop a drilling technique to sample from a horizontal hole up to 
1,000 ft. (305 m) in depth. It was anticipated that the "sample borer" 
would be employed in conjunction with a tunnel-boring machine during 
operation. This requirement dictated a drilling technique with a rapid 
penetration rate. It was further stipulated that only "moderately strong 
rock" and "high strength rock" were to be considered. The report 
defined rocks in this range as having uniaxial compressive strengths 
from 10,000 to 30,000 psi. (6.9 x 10 7 to 20.7 x 10 7 N/m 2 ) A Phase 
I report was issued in April of 1972 which was in essence an evaluation 
of techniques to determine which drilling methods should be employed 



5-9 



PENETRATION METHODS 





a) 




rCJ 




u 




d 


u 


•H 


(1) 






<N 


<u 


1—1 


6 


O 


rt 





CD 
,d 

o 
n d 

J) -H 
CO 

So 



CO 

CD 

rd 

o 
d 

<W ~ 
+> v£> 

CD (M 

§5 

co -4-> 



I Q -| at I 






H 



w 60 

§.S 

CD fn 
& Q 



O "5 H 



QQ 



"3 ti 



s s - s 



cd o £ 

d d o 



-M ,d 



£ ° d " 



d fh 

•H 

-d d 

o a 



o ^ 

O f\J 

-r- 



■B * 

00 

CD 



o — • 
o ^ 
o P 

« CO 



O CM 

o un 

ID r-l 



5-10 



in a subsequent field test program. Rolling cutter bits, diamond 
wireling coring, and down-hole percussive drilling were recommended 
for the test program. The test results were presented in a Phase II 
report dated October 1972. A down-hole percussive technique with 
intermittent diamond coring was selected as the drilling method which 
came closest to meeting the program requirements. The longest hole 
drilled was 864 ft. (263 m) long and 4 inches (102 mm) in diameter. 
The results of this test are referenced elsewhere in this report with 
regard to the particular methodologies employed. Of particular interest 
is a novel method of handling 1, 000 ft. (3 05 m) of drill rod at up to 
200 fpm (1. 01 m/sec) which was developed and tested during the 
program. 

In March 1973 Fennix and Scisson, Inc. of 
Tulsa, Oklahoma reported on a Bureau of Mines contract on Advanced 
Techniques for Drilling 1, 000 ft. Small Diameter Horizontal Holes in a 
Coal Seam. ' The goal of this contract was to "demonstrate in the 
field the control devices and techniques applicable to drilling 3 -inch 
diameter, horizontal holes with enough accuracy to stay within a coal 
seam and come within 3 ft. of a designated point at a depth of 1,000 
ft. " There was no requirement for geological sampling. This report 

included a state-of-the-art review of drilling long horizontal holes, 
including discussions on equipment and methods. The longest hole 
drilled for this contract was a 1, 102 ft. (336 m) long, 3.5 inch (89 mm) 
hole drilled with a rolling cutter bit and a custom built drilling rig. 
The results of the Fennis and Scisson work are referenced elsewhere 
in this report where they apply to particular methodologies. 

The Bureau of' Mines has continued research on 
horizontal drilling for coal degasification. The Bureau has now drilled 
horiztonal holes up to 2, 126 ft. (648 m) in length. (As of Sept. 1975) 
A Bureau of Mines Report of Investigation titled, Rotary Drilling of 
Holes in Coal Beds for Degasification by Cervik, Fields, and Aul is 
expected to be published in October, 1975. This document is intended 
to serve as a detailed horizontal drilling handbook for rotary drilling 
in coal. 



5-11 



In a May 1974 report, Fennix and Scisson, Inc. 

presented the results of a study titled, Improved Subsurface Investigation 

for Highway Tunnel Design and Construction. Volume I. Subsurface 

4 
Investigation System Planning . This report has a section on Horizontal 

Long Hole Drilling which (1) reviews the state-of-the-art of long horizontal 

drilling, (2) compares horizontal penetration techniques, and (3) discusses 

the feasibility of drilling long horizontal holes. This report makes the 

following selection of "best potential systems:" 

"The following are examples of rotary drilling 
assemblies that have been or could be used to drill long horizontal holes 
in soil and rock. To date, only assemblies A & B have been used to 
successfully directionally drill a straight horizontal hole longer than 
3,000 feet and only assembly A has been used to drill a horizontal hole 

one mile long. 

I. Existing Equipment and Technology Developed 

A. Standard rotary non- coring assembly 

1. Rotary bit designed for type and hardness of 
material to be penetrated. 

2. Stabilization designed for maximum horizontal 
and vertical directional control. 

3. Non- magnetic survey assembly. 

4. Rigid drill pipe to surface. 

B.- Standard rotary wireline diamond coring assembly 

1. Rotary diamond coring bit. 

2. Wireline coring assembly. 

3. Reaming shells and stabilizers designed for 
maximum vertical and horizontal directional 
control. 

4. Non- magnetic survey assembly. 

5. Rigid drill pipe to surface. 



5-12 



C. Continuous coring assembly 

1. Rotary diamond coring bit. 

2. Reaming shells and stabilizers designed 
for maximum vertical and horizontal 
directional control. 

3. Non-magnetic survey assembly. 

4. Rigid dual wall pipe to surface for 
continuous ejected core. 

D. In-Hole Motor 

1. Rotary bit designed for hardness of 
material to be penetrated. 

2. In-hole, positive displacement mud motor 
with or without bent sub or bent housing. 

3.- Optional stabilization. 

4. Non-magnetic survey assembly. 

4 

5. Rigid drill pipe to surface. " 

5. 4. 2 State -of- the -Art Horizontal Drilling Methods 

Specific criteria for evaluating candidate horizontal 
drilling methods are presented in Section 5. 1. The general criterion of 
state-of-the-art is defined in the discussion which follows. Since the term 
state-of-the-art implies techniques which are available and proven, state- 
of-the-art horizontal drilling methodology is defined in terms of available 
production hardware and procedures which have been proven in horizontal 
drilling applications. Custom equipment, proprietary or government 
sponsored experimental equipment and the procedures associated with its 
use, and production equipment which has not been applied to horizontal 
drilling are not considered state-of-the-art. However, custom, exper- 
imental, and conceptual equipment and procedures, as well as the mod- 
ification of available production equipment to function in horizontal drill- 
ing, will be discussed in relation to "next generation" drilling capabilities. 



5-13 



On the basis of the above criteria, the following tech- 
niques are considered state-of-the-art horizontal drilling methods: 

(1) Diamond wireline core drilling. 

(2) Rotary drilling (with rolling cutter bits) 

(3) Down-hole motor drilling. 

(4) Down- hole percussive drilling. 

This list does not include several of the horizontal penetration techniques 
which have been proposed in prior studies. The reasons for this are as 
follows. Rotary drilling with drag bits, discussed in reference 8 (Set 
Figure 5. 2), is eliminated from consideration because drag bits are 
limited to applications in soils and soft rock. Machine tunneling, which 
is also evaluated in reference 8 (See Figure 5. 2), is, of course, not a 
drilling technique and produces holes of far greater diameter than the 
sizes considered in this study. The continuous coring technique, 
suggested in the May 1974 Fennis and Scisson report, is not considered 
state-of-the-art because, as noted in that report, "so far as is known, 
this technique has not as yet been adapted to drilling horizontal holes. " 
Evidence of one such application has in fact been obtained (See Item 11, 
Table 2. 1) but the details available on this work are too sketchy to support 
consideration of the technique as state-of-the-art horizontal drilling method. 
This technique is discussed in detail in Section 6 as a promising next 
generation drilling and information gathering method. 

The four candidate drilling methods all fit the general- 
ized flow diagram of Figure 5.1. However, only diamond wireline core 
drilling is able to create a hole and gather cores simultaneously. If one of 
the other three techniques is to be employed, and core samples are needed, 
the drilling assembly must be replaced by a coring assembly when cores 
are taken. This increases the amount of drill rod handling required for these 
techniques. 



5-14 



In the following section, horizontal drilling method- 
ology is described in detail and the capabilities of the state-of-the-art of 
horizontal drilling are assessed. 



5-15 



6. Horizontal Drilling Methodology 

6. 1 Drilling Methods 

6.1.1 Diamond Wireline Core Drilling 

Diamond core drilling is an attritivc material dis- 
engagement in which rock is ground away by abrasive action. The drill 
bit is made up of diamonds set in a matrix material. The bit cuts an 
annulus in the rock, leaving a central core which is collected in a core 
barrel as the bit advances. The core barrel is retrieved when it becomes 

full. The procedure is depicted in Figure 6. 1 and Figures 6. 2 thru 6. 5 

illustrate wireline drilling equipment. 

There are in fact two methods of diamond core 
drilling. In conventional core drilling the core barrel is attached to the 
end of the drill string, requiring that the entire drill string be withdrawn 
from the hole to recover the core and install an empty core barrel. In 
wireline core drilling, the core barrels are pumped down the center of 
the drill string and retrieved on a wireline when they are full. Since 
wireline core drilling does not require that the drill string be pulled 
from the hole when cores are recovered it is clearly the preferred 
method for drilling long holes. 

As noted previously, diamond core drilling is the 
only candidate drilling method which creates a hole and provides core 
samples simultaneously. There are full hole diamond bits, however, 

the full hole bits give lower penetration rates and higher bit costs 

than core bits of the same outside diameter. 

Diamond wireline core drilling is employed in both 
the mining and petroleum drilling fields. Wireline core drilling in the 
mining field involves complete drilling systems from surface rigs to bits. 



6-1 



In the petroleum industry, wireline core drilling is employed as a 
technique for obtaining intermittent core samples, from a. hole which 
is being drilled primarily by rolling cutter bits. Wireline equipment 
for petroleum drilling includes bits and core barrels rather than 
complete drilling systems, and is made for much larger hole diameters 
than wireline equipment for mining applications. Generally, the two 
fields involve an entirely different list of equipment manufacturers 
and contractors. Christensen Diamond Products Co. of Salt Lake 
City, Utah is one of the few companies involved in both fields. 

The discussion which follows applies to diamond wireline 
core drilling with what, is generally termed mining or exploration equip- 
ment. Procedures applied to petroleum drilling are discussed in Section 6.6. 

6.1.1.1 Operating Procedures 

Diamond wireline core drilling procedures are 
illustrated schematically in Figure 6.1. The general procedural diagram 
of Figure 5.1 applies to wireline core drilling and all other conventional 
techniques. The drill must be aligned with a level or transit and firmly- 
anchored in place. A concrete pad should be constructed to support the 
surface rig. An initial length of hole is drilled and cased to bedrock to 
provide a secure and accurate starting point and a stuffing box is attached 
to the casing to control the flow of the drilling fluid. 

As the bit advances, the material disengaged 
by the bit is flushed from the hole. Water and drilling muds have been 
used for chip removal in horizontal wireline core drilling. The drilling 
fluid is pumped down the center of the drill string to the bit, where it 
washes the hole face and carries the rock debris out of the hole through 
the annular space between the hole wall and the outside of the drill rods. 
New sections of drill rod are added as the hole advances. When the hole 
has advanced far enough to fill the core barrel, a device called an over 
shot is pumped down the drill string where it latches on to the core 
barrel. The core barrel is then retrieved on a wireline attached to the 
overshot, and an empty core barrel is run down the drill string. 




6-3 



The drill string is pulled from the hole to 
replace the bit when it becomes worn. 

6.1.1.2 Equipment 

A general equipment and materials list for 
diamond wireline core drilling is presented in Table 6.1. The following 
discussion describes the primary elements of the drilling system, namely, 
(1) the drill rig, (2) drill rod, (3) overshot and core barrel assemblies, 
and (4) bits. (Figures 6. 2 thru 6. 5) 

Typical diamond core drilling rigs may be 
powered by gasoline or diesel engines, compressed air, or electric 
motors. The swivel head rotates 360° and has either a manual or 
hydraulic (automatic) chuck. The drill rods pass thru the chuck and a 
water swivel is attached to the outboard end of the rod. This swivel is 
removed and reinstalled when drill rod sections are added. The drill 
string is gripped by the chuck, the chuck is driven forward by a pair 
of hydraulic cylinders, the chuck disengages from the rod and is re- 
tracted by the cylinders, and the cycle is repeated. A diamond drilling 
rig is illustrated in Figure 6.2. 

A letter code designation is used to indi- 
cate compatible systems of down- hole wireline equipment. The first letter 
of the codes refers to the outside diameter of the hole produced by a given 
series. A table of hole outside diameters corresponding to the letter 
designation codes is presented in Table 6.2, The equipment discussion 
which follows will refer to equipment sizes by these letter designations. 

Wireline drill rods are available in the A 
to P sizes and in- 5, 10, and 20 foot (1.5, 3.1, 6.1 m) lengths. The 
newer designs used cold drawn seamless steel tubing for the rod body 
with alloy steel sections added at each end for the male (pin) and female 
(box) thread connections. 



6-4 



Table 6.1 - General Equipment and Materials List for Diamond 
Wireline Core Drilling 

Item Description 



(a) 


Drill 


(b) 


Circulating Pump 


(c) 


Supply pump 


(d) 


Hydraulic Ram 


(e) 


Generator and Lights 


(f) 


Mud Tanks 


(g) 


Mud Mixer 


(h) 


Core barrel assembly 


(i) 


Overshot assembly 


(J) 


Wireline 


(k) 


Drill rod 


(1) 


Outer core barrel tube 


(m) 


Inner core barrel tube 


(n) 


Survey instrument 


(o) 


Diamond core bits and 




reaming shells 


(P) 


Drilling mud 


(q) 


Grout 



6-5 



llS^a 




if s 


fl 




<u 


° 


B 




Ph 




• H '3 


(0 c i» 


"pj a 1 


1-1 


W 


* o ^ 


bJO 


~ g* 


fi bO 


l£ 


3 fl 




Vi r^ 




Q ^ 
Q 




Xi 




fl T3 




S 




rt £ 


tomotive 
erfaces 


a s 






<dui 


CO 


mS 


CM <U 






|l 


^'| 


O 


aj pq 




h 




53 ~ 




DJO >> 




iH CO 




PH 0) 




-P 




h 




3 









U 



6-6 



Table 6. 2 - Diamond Core Drilling Hole Dimensions 



Size 


Hole Diameter 


Inches 


mm 


R 


1. 175 


29.8 


E 


1.485 


37.7 


A 


1.890 


48.0 


B 


2.360 


60.0 


N 


2.980 


75.7 


H 


3.782-3.907 


96.0-99.2 


P 


4.827 


122.6 



6-7 



Wireline core barrels and overshots are 
available in the A thru P sizes. The core barrels come in 5, 10, 15, 
and 20 foot (1.5, 3.1, 4.6, 6.1 m) lengths. An N size overshot and 
core barrel are illustrated in Figures 6.3 and 6.4 respectively. 

A diamond coring bit is illustrated in 
Figure 6.5. Most exploratory drilling and all long horizontal drilling 
has been done with bits in the A to N sizes. However, wireline bits 
up to P size are available. As noted previously, the bits used in 
petroleum applications are much larger, running to 12.25 inches (311 mm) 
outside diameter. 

Diamond wireline drilling equipment manu- 
facturers and drilling contractors are listed in Appendix A. Among the 
major U. S. equipment manufacturers are Acker Drill Company, Inc. 
and Sprague and Henwood Inc., both of Scranton, Pennsylvania, Boyles 
Operations of Ontario, Canada, Christensen Diamond Products of Salt 
Lake City, Utah, Joy Manufacturing Co. of Claremont, New Hampshire, 
and Longyear Company of Minneapolis, Minnesota. Among the contractors, 
Longyear Co. , Boyles Bros. Drilling Co. of Salt Lake City, Utah, 
Reynolds Electrical and Engineering Co. of Las Vegas, Nevada, and 
Sprague and Henwood have experience in long horizontal core drilling. 



6.1.1.3 Capabilities 

Ideally, the horizontal penetration capa- 
bility of diamond wireline core drilling could be determined by comparing 
bit thrust and torque requirements with surface rig thrust and torque 
outputs on the basis of the efficiency with which energy is transmitted 
from the rig to the bit. Unfortunately, data is not available on energy 
transmission efficiency in horizontal drilling and procedures have not 
been developed to calculate such data. Therefore, energy transmission 
efficiency must be inferred from case histories and educated guesses. 



6-8 




®r~' 



®r 






S> ; 



NQ Overshot Assembly 



01-20 28033 Complete Overshot Assy 




335 


15.1 


01 


25987 Cable Clamp 








02 


25988 Wire Rope Thimble 








03 


25991 Eye Bolt 








04 


25990 Cable Swivel Collar 








05 


25986 Needle Thrust Bearing 








06 


25985 Castle Nut 








07 


Coml Cotter Pin 3/32" X 3/4" 








08 


17447 Grease Fitting 








09 


27477 Body 




2.1 


.9 


10 


22917 Hex Stop Nut 1/2-13 Unc 








11 


20013 Jar Tube 




17.7 


8.0 


12 


14653 Jar Head 








13 


15965 Locking Sleeve 




3.5 


1.6 


14 


14654 Jar Staff Assy 

15371 For Spare Or Replacement 


Shear Pins 


2.5 


1.1 


15 


27747 Machine Screw 1/4-20 Unc 


3/8 Lg 






16 


26608 Overshot Head 




4.2 


1.9 


17 


15373 Lifting Dog Spring 








18 


25980 Pivot Pin Lifting Dog 








19 


24307 Spring Pin 1/4" Dia X 2 In 


Lg 






20 


14651 Lifting Dog 


2 1.0 


.5 



NQ-U Conversion Kit 



1 Weighs less than one pound (.45 kg) 



The NQ Core Barrel can be easily converted to an NQ-U Core Barrel by 
means of an NQ-U Conversion Kit. The Kit comes assembled, ready for 
installation. Only the ball check spring, ball, locking coupling and drive 
coupling come as separate components. Order kit part number: 



••26108 NQ-U Conversion Kit 



Note: NQ-U overshot must al 
i Not generally carried in stock 



! ordered for i 



24.8 



\ above kit. See page 16 Section I 



Figure 6. 3 - NQ Overshot Assembly 
(Courtesy, Acker Drill Company, Inc. ) 



6-9 



®- 



®^. 



.-® 



-® 



4-® 



l><33) 



NQ Wire Line 



Name of Part 



01-45 24907 Core Barrel Assy 5-Ft 


95 


43.0 


01-45 24876 Core Barrel Assy 10-Ft 


139 


62.9 


01-45 24911 Core Barrel Assy 15-Ft 


183 


82.9 


01-33 24908 Inner Tube Assy 5-Ft 


38 


17.1 


01-33 24877 Inner Tube Assy 10-Ft 


47 


21.4 


01-33 24912 Inner Tube Assy 15-Ft 


56 


25.4 


01-20 24878 Head Assy 


21 


9.5 


01 


24879 Spearhead 


1 1.2 


.6 


02 


24880 Case Latch Retracting 


1 3.5 


1.6 


03 


24305 Pin Spring 1/2 In Dia X 2 In Lg 


2 




04 


24881 Spring 






05 


24882 Latch 


2 




06 


24548 Pin Spring 1/2 In Dia XI 1/2 In Lg 






07 


24883 Support Latch 






08 


22646 Pin Spring 1/4 In Dia XI 1/2 In Lg 






09 


24884 Body Latch 


1 6.1 


2.8 


10 


24885 Nut Lock 






11 


24886 Spindle Assy 


1 3.1 


1.4 


12 


24887 Valve Shut-Off 


2 




13 


24888 Washer Valve-Adjusting 


2 




14 


24312 Bearing Ball Thrust 






15 


24889 Bearing Spindle 


1 1.6 


.7 


16 


24313 Spring Compression 






17 


24314 Nut Self-Locking 




* 


18 


24890 Cap Inner Tube 


1 3.2 


1.5 


19 


17447 Grease Fitting Hydraulic 






20 


18298 Bearing Hanger 






30 


24909 Tube Inner 5-Ft 


1 12.3 


5.6 


30 


24891 Tube Inner 10-Ft 


1 24.5 


11,1 


30 


24913 Tube Inner 15-Ft 


1 36.8 


16.7 


31 


24892 Case Core Lifter 






32 


24893 Ring Stop 






33 


24894 Lifter Core 






40 


24895 Coupling Locking 


1 5.8 


2.6 


41 


24896 Coupling Adapter 


1 3.6 


1.6 


42 


24897 Ring Landing 






43 


24910 Tube Outer 5-Ft 


1 44 


20.0 


43 


24898 Tube Outer 10-Ft 


1 79 


35.9 


43 


24914 Tube Outer 15-Ft 


1 114 


51.8 


44 


24899 Stabilizer Inner Tube 






45 


24900 Protector Thread 


1 4.0 


1.8 



OPTIONAL ACCESSORY EQUIPMENT AND TOOLS 

(not shown) 



24315 Wrench 2 In Open-End 
24901 Blank Reaming Shell NQ 



■ Weighs less than one pound (.45 kg) 

CHROME PLATING. Hardness is 9 Moh's scale. To orde 



nber and specify "chrome plated" with 
21372 OUTER TUBE. 18" (46 ml 
each end, .004" (.1 mm) thick. 
21833 INNER TUBE. Entire inner surface, .002" - .004 



CP" to Core Barrel par 
er surface at both ends, 1/16" (1.6 mm) fron 
im) thick. 



NQ-U Conversion Kit (See r £ 



Figure 6.4 - NQ Wireline Core Barrel 
(Courtesy, Acker Drill Company, Inc. ) 



6-10 



HARD FACING (WEAR RETARDENT STRIPS) 

■BOX THREAD CONNECTION 

■O.D. BROACH MARKS (OUTSIDE) 



O.D. KICKER STONES 

O.D. GAGE STONES 



BLANK 



PAD ARE 




FACE STONES 
(PAD AREA) 



I.D. KIC 

STONES 



WATERWAY 
REINFORCEMENT 



GAGE STONES 



I.D. BROACH MARKS (INSIDE) 



Figure 6.5 - Diamond Core Bit 
(Courtesy, Christensen Diamond Products) 



6-11 



Nominal thrust requirements for diamond 

1 3 
coring bits can be obtained from manufacturers' data and corresponding 

torque requirements can be derived from analytical or empirical relation- 
ships. This has been done and the results are plotted as a function of 
bit size in Figures 6.6 and 6.7. Representative drill rig specifications 
have been obtained from manufacturers and are given in Table 6.3. 
Drill rig manufacturers are not consistant in terms of the specifications 
which they provide so some omissions are evident in this Table. Most 
of the listed rigs are available with a variety of power plant options 
so the table lists the maximum horsepower unit quoted in the company 
literature. The manufacturers do not list torque specifications for the 
rigs, therefore the figure in the table is derived from the maximum 
power plant output. This procedure can be expected to substantially 
overrate torque output. Torque is listed for 400 rpm which is a nominal 
recommended bit speed for N size bits. 

The horizontal drilling being carried on by 
the AEC at the Mercury, Nevada test site (item 4, Table 2.1) is the only 
sustained, well documented program of horizontal diamond wireline core 
drilling which has been conducted. This work is being performed in 
very soft (1,500 - 2,000 psi compressive strength) formations. Horizontal 
wireline drilling in harder materials (items 2, 3, and 5; Table 2.1) has 
been privately funded and the data on this work is very limited. The 
Longyear 44 drill has been used to drill 4,000 foot horizontal holes 
(items 2 and 3, Table 2.1) and Longyear Co. personnel are of the 

opinion that the unit is capable of drilling to 5,000 feet horizontally in 

14 
competent materials. 

The thrust necessary to move the drill 
string is proportional to f x w where: 

f = effective coefficient of friction 

w = effective drill string weight. 



6-12 



* 



30 



40 



(millimeters) 
50 60 



70 



•Ml ■ I ' 

Thrust versus Bit Size 
for Diamond Coring Bits 



80 



40 



§ 5 
o 



a 4 
o 



H 3 



Hard Formations 



EX 




30 



*°Z 



Soft Formations 



10 



**r 






12 3 

Bit Outside Diameter, inches 
Figure 6.6 - Coring Bit Thrust Requirements 



6-13 



(millimeters) 
A/ 30 40 50 60 70 80 

# — ' I ' I ■ I ' I ' I ' I 



500 



350 



Torque versus Bit Size for 
Diamond Coring Bits 



450 



300 



^ 250 



"pq 200 



° 150 



100 



50 



EX 




NX 



400 



350 



300 



250 



200 



150 



100 



50 



*r 



1 2 3 

Bit Outside Diameter, inches 



Figure 6.7 - Coring Bit Torque Requirements 



6-14 































































































o 














t- 




















































W 




















u 


PL,' 


' 


s 


' 


' 


• ' 


' 


CL 


' 


c 






X 




5 










o 

00 




H 


£-> 


IM 




m 










■* 








rt 


„ 












_; 
































■* 












i- 












o 










•* 








s 




























3 




o> 


CO 




















00 




H 




a' 








c 




00 






2 


1 


X 





o 


~ 




2, cs 


— 


sO 


M 




a 


N 


o 
o 


o 


z 





CO a- 


N 


°1 


rt 


f 


< 


" 


in 


(SJ 


~" 


X 






" H 


H 


■a 




































































£ 






















c 

1 



























£ 












CN 

c* 




«s 




6 


M? 


_ 






<* ~o 


Pj 


CO 














































rJ 


U 


X 


o 
o 




£ 





w ■"■ 




o 


XI 














o 










a 






SO 






vO 


o •* 


>0 




3 


to 


* 


m 


"■" 


■* 


IM 


m 


~" 


m 


(M 








o 




















_, 


CO 
































































J> 


£ 


~ 






?T 00 


3" 






| u 




Q 










■* ~a 


t- 










o 
















bo 






o 


S 


O 


o 


EL S 


~ 


















o 




vO 












)j 






vO 


o ■* 


vO 






J 


* 


*o 


t ~ 


N 


"° 


"■ 






to 


















































3 


m 




O 








~ 








o 














r~ 








s 


■* 




o" 




~ ~ 




"1 








a 


f> 


S' 


3 




5 S 




w 






Q 


PU 


o 


£ 


o 




2. ~ 




"" 






CO 


ffi 



















>> 












o 


o ■* 






















■* in 






J4 


^ 


N 


m 


"* 


in 


N 


en 


"* 




■* 


to 














































































vO 












































o 






































n! 


















^ 





ft 


. 


1 






■ ■ 


- 


■ 


























" 


to 


S 




rS 


* 











-0 


o 


« 


2 




ro 


■* 


o 








2 


a 


ffl 


•"■ 




- 




CO 








to 






s> 






















































































5 


o 


































00 




























3 













o ~o 










































in o 


O 
















-o 


































1 


•a 


"_ 


o 
o 


(M 


•1 


o 
o 


o o 


■* 


o 


T3 










■* 




o ■* 


O 




!? 


< 


2 


■o 


" 












(M 


to 


1 




























§ 
























































































■-* 


2 






"g 




_ 










a. 


o, -=■ 










Z 










o 


a S 


1 




— 








u ' 






o 
o 


o 
o 


— 




.3 




^ 




9 

3 

n) 

■g 
S 
a 




M 


-«" 


* Z 




Si 


a 








■a 
o 

a 


o 

0, 


.c 
H 


f ii 
o 


1 

to 


c 

G 

<! 


.I ^ ^ 
Q 


DO 

u 

X 


1 


00 

.5 
c 
o 

2 



The torque required to turn the string is proportional to 0.5 D x f x w 
where D equals the hole diameter. 

Figure 6.8 plots the ratio of thrust to 
torque output required to overcome drill string friction against hole 
size. The output ratios for the drill rigs listed in Table 6.3 are also 
included on the plot. This indicates that, for horizontal applications, 
available surface rigs are torque limited rat her than thrust limited. If 
the rig torque outputs from Table 6.3 are compared with the drill rod 
data of Table 6.4, it is also clear that penetration capability is surface 

rig limited rather than drill string limited. This agrees with the 

14 
assumptions of drilling contractors. 

If the manufacturer's assessment that the 
Longyear 44 machine is capable of drilling holes to 5,000 ft (1524 m) 
in the B size is accepted, then the capabilities of other machines can 
be inferred by comparing their output to the Longyear machine. This 
suggests that the Boyles BBS- 56 machine is capable of drilling to 9,200 ft 
(2804 m). However, the total horizontal drilling task involves many more 
variables than surface rig torque output. Based upon available data and 
detailed interviews with drilling contractors and equipment manufacturers 
5,000 ft (1,524 m) appears to be a reasonable assessment of the max- 
imum penetration capability of state-of-the-art wireline core drilling 
equipment for a B size bit. 

The lower limit on hole size is determined by 
the 1.75 inch (44.5 mm) outside diameter of available hole survey tools. 
These devices cannot be run in rods smaller than B size (1.8125 inch 
(46 mm) inside diameter). Diamond wireline drilling is not common in 
sizes above N, primarily due to cost considerations. Available equip- 
ment in the larger H and P sizes is limited and the equipment has not 
"been applied to long horizontal drilling. Therefore, the N size should be 
considered the upper limit for diamond wireline core drilling. 



6-16 



24 
(78) 

22 
(72) 

20 
(66) 

S 18 

$ 16 
- (52) 




Standard 
Drill Rigs 
(Torque 
Limited) 



§ 14 
2* (46) 

o 

H 12 
3(39) 



3 io 

£(33) 

H 

°(26) 



«J 6 
(20) 

4 
(13) 

2 

(6.6) 




AARDVARK H 



-I (Thrust 
Limited) 



1(25) 



2(51) 3(76) 

Hole Size, inches (mm) 



4(102) 



5(127) 



Figure 6.8 - Ratio of Thrust Friction to Torque Friction 
as a Function of Hole Size 



6-17 







TABLE 6.4 










DRILL ROD DATA 




Size 


OD, in. (mm) 


ID, in. (mm) 


Minimum 

Yield 
Strength, 2 
psi ( N/m ) 


Maximum 
Torque, 
Ft. lb. 
(N • m) ! 
i 


AQ 


1.75 (44.5) 


1.438 (36.5) 


15. 000 
(103,425,000) 


716 (971) 


BQ 


2.1875 (55.6) 


1.875 (47.6) 


15,000 
(103,425,000) 


1182 (1603) 


NQ 


2.75 (69.9) 


2.4375 (61.9) 


15,000 
(103,425,000) 


1954 (2650) 



6-18 



(sja^auiijircu) 





t 1 


1 1 


o 






o 






ID 


- / 




■— I 


A 












0} 








S o 






■"■ 


5 <=> 








<5 o 








1 " 




00 


— 






Q 


— 






a) 








^ 








o 








U 


■~~ 


o 




0) 




o 




(h 




in 












T3 


— 






a 








O 








s 








5 


_ 












_i— 


Q 
1 


1,1! 



saxpux 'ja^stu-exQ axon 



h 



6-19 



State-of-the-art penetration capabilities 
are illustrated graphically in Figure 6.9. The penetration capability 
for the N size was determined from the simplified assumption energy 
transmission efficiency will be reduced in proportion to drill rod weight 
for a fixed drill rig output. 

6.1.2 Rotary Drilling (Rolling Cutter Bits) 

Rotary drilling techniques were developed primarily 
for drilling petroleum wells but they are now also widely used in blast- 
hole drilling. A typical rotary drilling setup for vertical drilling is 
illustrated in Figure 6.10. Note that the bit thrust is generated by the 
heavy collars which make up the drill string immediately above the bit. 
The drill collar weight exceeds bit thrust requirements so that the drill 
pipe portion of the drill string is always in tension. When rotary 
drilling techniques are applied to horizontal drilling two factors are 
immediately apparent. (See Figure 6.11.) First, the bit thrust must 
now be applied to the bit by the surface drilling unit and second, the 
entire drill string is now in compression. These two facts are the 
primary reasons that preclude "turning petroleum technology on its 
side',' to drill long horizontal holes. 

To apply rotary drilling techniques to horizontal 
drilling (1) drill rigs must be developed which have the capability of 
providing the necessary thrust forces to the drill string and (2) pro- 
cedures and equipment must be developed to minimize drill string 
buckling. Very little work has been done in either area. 

With rolling cutter bits, material disengagement 
is accomplished with a crushing action. Heavy thrust and continuous 
rotation are applied to the bit, causing the bit teeth to crush and 
fragment the rock. In similar materials, the thrust and torque 



6-20 




Figure 6. 10 - Vertical Rotary Drilling 



6-21 




6-22 



required for rolling cutter bits far exceeds that required for diamond 

bits of the same diameter. Rolling cutter bits are available for materials 

ranging from very soft to very hard. (See Figures 6. 12 and 6. 13) 

Rolling cutter bits are generally full hole bits. 
Some effort has been made to develop rolling cutter coring bits, but 
these efforts have been largely experimental and they have not been 
applied to horizontal drilling. The use of rolling cutter bits for 

coring is discussed further in Section 6.6. 

6.1.2.1 Operating Procedures 

The procedures employed in horizontal 
rotary drilling are similar to the procedures employed in horizontal 
wireline core drilling. The only significant difference between the two 
techniques, in a procedural sense, is that rotary drilling does not in- 
clude coring procedures. If coring is required in horizontal rotary 
drilling, diamond coring techniques must be employed for the length of 
hole where cores are needed. 

Air, water, and drilling mud are used as 
chip removal fluids in vertical rotary drilling but water or drilling mud 
would be more likely in horizontal applications. 

6.1.2.2 Equipment 

An equipment and materials list for hori- 
zontal rotary drilling is presented in Table 6.5. The following dis- 
cussion concerns drilling rigs and bits. 

There is only one drilling rig made 
specifically for long horizontal rotary drilling. This unit is the Koken 
FS400 manufactured by Koken Boring Co. , Ltd, of Tokyo, Japan. 



6-23 



Table 6.5 - General Equipment and Materials List for 
Horizontal Rotary Drilling 



Item Description 



(a) 


Drill 


(b) 


Survey collars 


(c) 


Circulating pump 


(d) 


Supply pump 


(e) 


Hydraulic Ram 


(f) . 


Generator and Lights 


(g) 


Mud tanks 


(h) 


Mud mixer 


(i) 


Drill rod 


(J) 


Survey instrument 


(k) 


Rolling cutter bits 


(1) 


Drilling mud 


(m) 


Grout 



6-24 



Specifications for this unit are listed in Table 6. 6. Two applications 
of the unit are listed in Table 2. 1. (Items 1 and 12). Problems en- 
countered in attempting to obtain detailed infomaation on this rig suggest 
that it may not be readily available. 

Horizontal rotary drilling in the United 
States has been limited to soft (coal) and very soft materials. (See 
Table 2.1.) Heavy duty diamond drilling rigs or custom made rigs have 
been used in most of this work. (Items 7, 15, and 17, Table 2.1.) 
None of these units have thrust and torque capabilities compatible with 
rotary drilling in harder materials. 

Raise boring machines have been suggested 
as candidate drilling rigs for horizontal drilling rock. Specifications 

for a Dresser Model 300 raise borer are included in Table 6.6. This 
unit is manufactured by the Mining Services and Equipment Division of 
Dresser Industries, Inc., Dallas, Texas. Other raise boring machine 
manufacturers are listed in Appendix I. Raise borers would require 
modification in order to be used as horizontal rotary drilling machines, 
and a development effort would be required in order to develop pro- 
cedures for their use. However, they are strong candidates for "next 
generation" horizontal rotary drilling. Rotary blast hole drilling rigs can 
also be "repackaged" to perform as horizontal rotary drilling machines. 

There is a class of equipment which has 
been developed- for boring small utility tunnels beneath streets, highways, 
railways, and other structures where cut-and- cover techniques are not 
practical. This equipment is used to bore in rock with boring heads 

which employ toothed rolling cutter bits. State-of-the-art efforts in this 
field have been limited to lengths under 500 ft (152 m) and diameters from 
15 to 72 inches (381 - 1829 mm) The equipment used in this field may 

also be adaptable for drilling long horizontal holes in smaller diameters. 

Rolling cutter bits are available in diameters 
from 3.75 to .26 inches (95 - 660 mm). 



6-25 



Table 6. 6 - Rotary Drilling Rig Specifications 



Manufacturer 


Koken Boring Machine 


Dresser 
Industries 


Model 


FS-400 


300 


Power Unit 


400 H. P. Electric 


75 H. P. Electric 


Thrust, lb (N) 


88,000 (391,424) 


90,000 (400,320) 


Pull, lb (N) 


110,000 (489,280) 


180,000 (800,640) 


Torque, ft -lb 

(N-m) 


16,420 (22,266) 
0-50 rpm 


22,000 - 6565 
(29,832 - 8902) 


Stroke, ft (m) 


18.4 (5. 6) 


RPM - 60 RPM 


Angle Range 


Horizontal 


90° to 20° 

(90° = Vertical) 


Dimensions 






Height, ft (m) 


6.2 (1.9) 


9.4 (2.86) 


Width 


5.1 (1.6) 


3. 58 (1.09) 


Length 


35.9 (10.9) 


9.83 (3.02) 


Weight, lb (N) 


28,600 (127,213) 


15,300 (68,054) 



6-26 



Bits may be of the milled- tooth type (Figure 
6.12) or the insert type (Figure 6.13) milled- tooth cutters are manufactured 
from heat-treated alloy steels in which rows of teeth have been cut from 
the outside of a cone. Milled-tooth cutters generally are limited to rocks 
in the soft to medium- hard range. The milled-tooth cutter is generally 
much cheaper than a comparable insert cutter. 

Insert cutters consist of a series of tungsten 
carbide inserts pressed into a cutter cone. The greater operating life 
of the insert cutter can frequently give it an economic advantage over 
the milled tooth cutter, particularly in harder materials. 

Rolling cutter bit manufacturers are listed 
in Appendix A. Listings of manufacturers supplying other rotary drilling 
supplies can be found by consulting the references noted in Appendix A. 

6.1.2.3 Capabilities 

In rotary drilling with rolling cutter bits, 
the requirement to be able to drill hard rock establishes a lower limit on 
hole size. The following observation was made concerning drilling hard 
rock with rolling cutter bits in the Jacobs Associates program.; 



"Drilling could not be accomplished in 
the hard rock at the Aromas site with the 4-1/4 in., three- cone steel 
tooth bit because it was impossible to apply sufficient thrust. The drill 
rig is limited to about 15,000 lb maximum thrust, as are most of the 
available small rotary rigs designed primarily for diamond drilling. 
There was no way to measure the net thrust achieved at the bit through 
the rather flexible drill rod. It is believed to have been less than half 
the minimum 20,000 lb required for this bit size in rotary drilling in 
hard rock. As a result of this it can be concluded that it will not be 
economical to design a drilling method using rolling cutter bits for 



6-27 




9" "Rotablast" Type S 
rock bit 



Figure 6.12 - Milled-Tooth Rolling Cutter Bit 
(Courtesy, Hughes Tool Co. ) 



6-28 




9V 8 " "Rotablast" Type HH 77 
rock bit 



Figure 6.13 - Insert Rolling Cutter Bit 
(Courtesy, Hughes Tool Co.) 



6-29 



horizontal holes more than 100 ft deep with a bit smaller than 7 in. 

12 
Rods for smaller hole sizes will be too limber." 



In addition to the problem of drill rod 
stiffness noted above, the life of rolling cutter bits for hard rock is 
limited by the bearing capacity which can be built into the bits as size 
is decreased. Williamson reported a bit life of "several inches" in 
trying to drill hard abrasive rock with a 4.2 5 inch (108 mm) roller bit. 
Typically, roller bits designed for hard rock are above 6 inches (152 mm) 

in diameter. For example, Hughes blast hole bit catalog does not list 

1 8 
tungsten carbide bits below 6.75 inches (172 mm) in diameter. The 

improvement in roller bit economy with size is evident in one reference 

which notes a 50 percent improvement in bit economy in going from a 

6.25 inch (159 mm) diameter bit to a 9 inch (229 mm) diameter bit in 

Q 

blast hole applications. In the petroleum industry the 7.875 (200 mm) 
and 8.5 inch (216 mm) diameter bit sizes are most common. In this 

case the economies of smaller casing apparently outweigh the economies 
of larger bit sizes. In blast hole applications casing is not a requirement. 
In order to accommodate the range of rock strengths anticipated in drilling 
along tunnel alignments, a 6.75 inch (172 mm) diameter hole size is 
recommended as the minimum for horizontal rotary drilling. 

The upper limit on hole size and the 
penetration capabilities of horizontal rotary drilling are limited by the 
available surface rigs. Nominal bit thrust and torque requirements for 
rolling cutter bits are presented in Figures 6.14 and 6.15. A comparison 
of the bit thrust requirements with the thrust output of the diamond 
drilling rigs listed in Table 6.3 indicates why diamond drilling rigs are 
not suitable as horizontal rotary drilling rigs for harder materials. In 
addition, the rotational speed and torque output of the diamond rigs are 
not suited to rolling cutter bits. 



6-30 



(N 000 'I) 



-' 1 


1 1 1 1 1 




1 ■ 


1 


1 1 


r ■ 


p / 






t 






— 


a. 














°0. 














o 
















«» 










- 












- 




\ 














\ 














\ 










■ 


— 


\ 

\ 

\ 

v \ 

\ \ 

X N 

X \ 
x N> 

X N 

X \ 

X N 








\ o 

\ ° 
V 


- 


- h 


V 








\\ 
\ 


- 


o 


V 


















X 

\ 








# 


V 






\ 






2 


K 






\ 
\ 
\ 

\ 






en 










\ \ 


■• 


3 










N \ 




m m 










S \ 




S " 










N \ 




<u .h 














>CQ 














-*-» k 














W (U 












\ m 


25 


























\ - 


1 I 


— 1 J 1 1 1 


. 


—J. 1 


„. A- 


1 1 


, 



- ^ 



o 


o 


o 


o 


o 


O 


o 


o 


o 


o 


o 


oo 


r^ 


vD 


tn 


^ 


CO 


CM 



SC IT 000'T ' *T9 uo isnjqj. 



6-31 



r^ 



150 



7 |— Torque Versus Bit 
Size for Rolling 
Cutter Bits 



6 - 



o 
§4 



175 

"T 



(millimeters) 
200 225 250 



275 




300 

T 



35 rpm 



/> 



Hard Formations 
/ Typical 



90 rpm 



cT, 



65 rpm 



0- 

^ZOO rpm 



1 50 rpm 



Soft Formations 
Typical 



- 2 



- 1 



Ltf-i L 



11 



12 



8 9 10 

Bit Size, inches 
Figure 6.15 - Rolling Cutter Bit Torque Requirements 



6-32 



The performance parameters of the Koken 

rig (Table 6.6) are suited to the requirements of rolling cutter bits. 

However, as in the case of diamond core drilling, there is no data 

available on the efficiency at which the output of the drilling rig is 

transmitted to the drill bit in horizontal drilling. The Koken machine 

is rated by the manufacturer to have a horizontal penetration capability 

of 6,600 ft (2000 m) when applied to rotary drilling. Available information 

indicates that the rig has been used to drill a 6.75 in. (171 mm) hole to 

4 
5,300 ft (1615 m) in soft materials. The manufacturer's assessment of 

penetration capability appears quite optimistic for harder materials. 

For example, the Longyear 44 diamond drilling rig has a ratio of torque 

and thrust output to bit requirements of about 5:1 and 4:1 respectively, 

in hard materials and a proven horizontal penetration capability of 4,000 

ft (1219 m). By contrast, the same ratios for the Koken machine with a 

6.75 inch (172 mm) bit are about 3:1. On the other hand, since the 

stiffness of the drill string increases in proportion to the fourth power of 

the diameter, it could be possible that the larger diameter drill string 

used in rotary drilling is less subject to buckling and thus more efficient 

in transmitting energy to the bit. In any case, given the lack of solid 

data on the efficiency of energy transmission in horizontal drilling, an 

assessment of a 5,000 ft (1524 m) penetration capability for a 6.75 inch 

(172 mm) hole is made for the Koken machine. The maximum thrust 

output of the Koken machine corresponds to maximum nominal bit thrust 

requirement (dotted line, Figure 6.14) for a bit diameter of about 12 inches 

(305 mm). This is assumed to represent the zero penetration rate capability 

for the Koken machine. Penetration capability for rotary drilling in diameters 

above 6.75 inches (152 mm) is projected from this assumption. 

The horizontal drilling capabilities of state- 
of-the-art rotary drilling equipment and procedures are presented 
graphically in Figure 6.16 along with the state-of-the-art capabilities of 
road crossing boring machines. 



»-33 



(s .t9;auix-[im*) 





1 ' 1 ' I 


1 1 ' 1 


I 1 ' 


o 








o 






— 


lO 










CO 




- 


O 


IS 






o 


— o 






o 


rt 








SI 

•S 


m 








•r4 






o 


CO 
CO 

o 


/ W) 
/ A 




o 


/ ,|H 




un 


n~ 5 


/ I— * 
/ H 






TJ 


/ Q 






rt 








o 


/ ^ 






(3 


/ h 

/ s 

/ o 

/ * 






1 1 1 1 1 1 1 1 1 


1 1 / 1 1 1 1 1 


1 1 1 1 1 1 



o 






o 






o 




>> 


LO 




2 

• H 


o 




U 


o 

o 




Pi 
o 


-* 














rt 






M 










■*-> 


CD 




V 


PI 




<D 


CD 


o 




Ph 


o 






o 

CO 


A 


W> 




PI 


Pi 




<D 


>— j 




-J 


Q 




CU 




o 


r— 1 

o 


>> 


o 
o 


ffi 




<M 






O 




PI 


o 




O 


o 




N 










saipm 'japuiBia a-[OH 



6-34 



6.1.3 Down-Hole Percussive Drilling 

In percussive drilling rock is fragmented by- 
repetitive impaction. The impacts are provided by an air-driven piston 
or "hammer 1 . 1 Drills are designed to index the bit between impacts so 
that a fresh rock surface is struck with each blow. 

Percussive drills are divided into two broad classes, 
drills for which the hammer remains at the surface and drills for which 
the hammer goes in the hole immediately behind the bit. Surface units 
lose effectiveness with hole length as the hammer impacts are attenuated 
by the drill string. This technique begins to lose effectiveness in holes 
beyond 100 feet (30.5 m) in length and would be essentially useless 
beyond 200 feet (61 m). The down-hole percussive drill is effective 
at longer distances and has been applied to horizontal drilling in a 
program conducted by Jacobs Associates of San Francisco, California. 10 

Percussive drills can drill soft, medium, and hard 
rocks, but they are most effective, relative to alternative techniques, in 
medium and hard rock. Air is blown down the center of the drill string 
to carry the rock debris from the hole through the annulus between the 
drill rods and the hole wall. A water and air mist is sometimes used 
for debris removal when drilling in sticky material. However, the 
effectiveness of percussive techniques is severely limited by the 
presence of ground water. 

6.1.3.1 Operating Procedures 

Procedures for horizontal drilling with 
down- hole percussive drills were developed and documented in the Jacobs 
Associates program referred to in the previous section. Figure 6.17, 
taken from the Jacobs report, indicates the equipment and procedures 
involved. 



6-35 




is? gi 



flLVUH 



m 






||K« g3§g 






i £ 



I i I 



* § 



I B 1 ? 



o 1 



© 

111 






©000®0®0@© 



6-36 



Mj£.. &&L. 



A modified Sprague and Henwood 40 CL 
diamond drilling rig was used to rotate and thrust on the drill string. 
Minimal thrust and torque input are required since the energy required 
to drill the rock is being produced by an air compressor and trans- 
mitted to the bit pneumatically. The air which powers the down- hole 
drill also serves as the flushing fluid for chip removal. Figure 6.17 
also shows the preassembled 1,100 ft (33 5 m) drill string and alternative 
wet flushing system used in the Jacobs program. This equipment 
allowed a rapid change to diamond coring procedures to obtain inter- 
mittent core samples. When core samples were required, (1) a rapid 
rod retractor was used to withdraw the drill string from the hole in a 
single piece, (2) the percussion drill was replaced with a double tube 
core barrel, (3) the rod retractor ran the drill string back into the 
hole, (4) water or drilling mud circulation was begun, and (5) core 
drilling operations commenced. After coring operations were com- 
pleted, the procedure was reversed and percussive drilling was continued. 

Apparently the only modification to the 
drill rig was the inclusion of a hydraulic drive unit between the engine 
and transmission. This allowed accurate torque figures to be computed 
and, in addition, provided a capability for stepless variation of rotational 
speed. 

Presumably the procedures employed in the 
Jacobs program could be applied with any similarly modified diamond 
drilling rig, and any down-hole percussive drill capable of operating in 
a horizontal orientation. 

6.1.3.2 Equipment 

Down- hole percussive drills are available 
in outside diameters ranging from 3.5 to 9 inches (89 - 229 mm). A 
drill unit is illustrated in Figure 6.18. Rated air consumption values 

for down- hole drills vary from manufacturer to manufacturer, but Table 

21 
6.7 presents approximate values. 

6-37 




Figure 6. 18 - Downhole Percussion Drill 



6-38 






Table 6.7 - Approximate Air Consumption for Down -Hole Percussion Drills 
(Does not include chip removal requirements) 



Hole Diam. 


Drilling 


ft /min 


m /mm 


3-3. 5 in (76-89 mm) 


80 


2. 26 


4 in (100 mm)' 


100 


2.83 


4.75-5 in (120-125 mm) 


150 


4. 25 


6. 25 in (158 mm) 


350 


10.00 


9 in (230 mm) 


600 


17.00 



6-39 



Bits for down-hole percussive drills are 
available in 4 to 12 inch (102 - 305 mm) diameters. Thrust require- 

ments for down- hole bits are low with thrusts of less than 2,000 lbs 

1 8 
(907 kg) being recommended for 6-7 inch (152 - 178 mm) bits. A 

typical percussion bit is illustrated in Figure 6.19. 

Down-hole percussive drill and bit manu- 
facturers are listed in Appendix A. Jacobs Associates used drills made 
by Inger soil- Rand and Mission Manufacturing Co. in their program. 

6.1.3.3 Capabilities 

Down- hole percussive drills are not 
designed for horizontal drilling, they are designed primarily for blast 
hole drilling in vertical and near vertical applications. The IngersoLL 
Rand-Model DHD14 performed satisfactorily in horizontal drilling, as 
did a unit made by Mission Manufacturing, but there is no experience to 
indicate whether other drills will or will not perform in a satisfactory 
manner in horizontal applications. 

The subject of drill guidance will be dis- 
cussed in more detail in Section 6.4, but it should be noted that there 
was no attempt to perform guided horizontal drilling in the Jacobs 
program. 

The capabilities of down- hole percussive 
drilling as a technique for drilling horizontal holes must be based on an 
assessment of the Jacobs Associates program since this program repre- 
sents the only source of data on this technique. On this basis, down- 
hole percussive techniques are classified as being suitable for horizontal 
penetrations to 1,000 feet (305 m) in hole diameters from 4 to 6 inches 
(102 - 152 mm). . Further development and testing are necessary to 
determine whether the entire range of available percussive drilling 
equipment is suitable for horizontal applications. The estimated hori- 
zontal drilling capabilities of this technique are presented graphically in 
Figure 6.20. 

6-40 











• •• 



o 



•^ 



o 



J 



o 

o 



o «o o 
o 





Figure 6. 19 - Percussion Bit 
(Courtesy, Hughes Tool Co. ) 



•41 



(s .is^auiTXlTtu) 




s£> ID ^ CO CM 



6-42 



6.1.4 Down-Hole Motor Drilling 

Down-hole motors do not represent a different class 
of material disengagement device but rather a different approach to pro- 
viding torque to diamond or rolling cutter bits. Down-hole motors apply 
torque directly at the bit, whereas the diamond and rolling cutter tech- 
niques discussed in Sections 6.1.1 and 6.1.2 provide torque to the bit by 
rotating the drill string from the surface. Electric motors, turbines, and 
positive displacement mud motors have been used as down-hole motors. 
However, the positive displacement mud motor (Dyna- Drill) manufactured 
by Dyna- Drill Co. , Long Beach, California appears to be the only down- 
hole motor device which has been successfully applied to long horizontal 
drilling. 

6.1:4.1 Operating Procedures 

Application of down- hole motors to hole 
straightening and hole deflection will be discussed in detail in Section 6.4. 

In a straight or curved horizontal drilling 
application the Dyna- Drill can be used with practically any surface rig which 
is capable of providing the necessary thrust to the drill string. The Joy 22, 
Koken FS400 and several Longyear Co. machines * have been used for hori- 
zontal drilling with the Dyna- Drill. (Items 1, 9, 10, 12, and 15; Table 2.1) 
The Dyna- Drill is driven hydraulically by a pump on the surface. Flow 
rate to the tool is adjusted to specified values and the thrust on the tool 
is adjusted until a pressure gage indicates that the recommended differential 
pressure exists across the motor. The pressure gage reading is directly 
related to the torque output of the motor. Increasing thrust will increase 
the pressure and torque and reducing thrust reduces both pressure and 



6-43 



torque. Therefore, the rig pressure gage monitors motor performance 
and serves as a drilling thrust indicator. Recommended operating pro- 
cedures for the Dyna-Drill and tables giving recommended flow rates, 
pressure drops, etc., for the various sizes are provided in the Dyna- 
Drill Handbook, 2nd Edition . 22 

6.1.4.2 Equipment 

The Dyna-Drill may be used with full- hole 
diamond bits, rolling cutter bits, and, in softer materials, drag bits. 
The diamond and rolling cutter bit manufacturers listed in Appendix A 
provide bits which can be used with the Dyna-Drill. 

Dyna- Drills are manufactured in 5, 6.5 and 
7.75 inch (127, 165, 197 mm) sizes for directional drilling and 5, 6.5, 7.75 
and 9.675 inch (127, 165,- 197, 245 mm) outside diameter models for 
straight hole drilling. Micro-Slim Dyna-Drill tools are available in 1.75, 
2.75, and 3.75 inch (45, 70, 95 mm) outside diameter models. The 1.75 
inch (45 mm) size (3 inch (76 mm) hole typical) and 5 inch (127 mm) sizes 
(6.75 inch (172 mm) hole typical) have been used in the horizontal drilling 
applications referenced in the previous section. The Dyna-Drill is illustrated 
in Figure 6.21. 

6.1.4.3 Capabilities 

The Japanese envision the use of down-hole 

motor techniques to drill holes to 15,000 feet horizontally. Both the 

Dyna-Drill and an electrically powered down-hole motor of Russian manu- 

23 24 
facture are reported to have been used in the Seikan Tunnel work. ' The 

best available evidence indicates that in actual use the longest range appli- 
cation of these devices, was the use of a 5 inch (127 mm) Dyna-Drill to 
control hole deflection between 3,325 feet (1013 m) and 3,895 feet (1187 m) 
in a 5,300 foot (1615 m) hole. 4 (Item 1, Table 2.1) 



6-44 



I Dump Valve Assembly 



2 Multistage Motor 





\ 



Figure 6. 2l - The Dyna-Drill Positive Displacement Down-Hole Motor 
(Courtesy, Dyna-Drill Co.) 



6-4! 



The 1. 75 inch (44 mm) tool has been used 
to drill to approximately 1, 600 feet (488 m) in soil and to 1, 700 feet 
(518 m) in a hole which was started essentially vertically and then curved 
to a horizontal trajectory in a coal seam. (Items 9 and 10, Table 2. 1) 
The 1. 75 inch (45 mm) tool has also been used successfully as a steering 
tool for horizontal drilling in coal. ' ' 

In assessing the horizontal drilling capa- 
bilities of down-hole motor techniques, which in terms of the state-of- 
the-art comes down to Dyna-Drill capabilities, one is faced with a 
great deal of speculation and very little documented "real world" ex- 
perience. This is true to a greater or lesser degree of all candidate 
horizontal drilling techniques. Keeping speculation to a minimum, the 
1. 75 inch (45 mm) tool can be considered a proven technique out to 
2,000 feet (609 m) and the 5 inch (127 mm) device out to 4,000 feet 
(1,219 m). No down-hole motor device, other than the Dyna-Drill, 
can realistically be considered a state-of-the-art tool for horizontal 
drilling. This capability assessment is illustrated graphically in Figure 
6. 22. 

6.1.5 Continuous Core Drilling 

Continuous core drilling or continuous ejected coring 
is a drilling technique using reverse circulation of the drilling fluid with 
a drill pipe consisting of two concentric tubes. The drilling fluid enters 
the hole through the annulus between the two pipes and returns in the 
center pipe carrying the drill cuttings and/or cores. 

Since the drilling fluid does not touch the hole wall, 
the technique is reputed to be very effective when drilling through loose, 
broken, or caving zones. Good recovery of weak, friable, or plastic 
cores is claimed. 

This technique may be used with diamond coring 
bits to allow continuous coring. (See Figure 6.23) The technique has 



6-46 



(sjs^auiTHFu) 




S81t[DUT 'JS^3UXBTQ 3T°H 



6-47 



the considerable advantage of allowing core to be taken continuously with- 
out interrupting the drilling operation. 

The two tube technique can also be used as a technique 
to gather geological data with drag bits, roller bits, and even down- hole 
hammer techniques. (See Figure 6.24) Since the chips return up the center 
of the drill string and are not contaminated through contact with the hole 
wall or by material eroded from the hole wall, they are a source of 
geological data on the area being drilled. 

Continuous coring drilling is a developed technique 
for vertical drilling but it has not been adapted to horizontal drilling. 
One instance of double tube, reverse circulation drilling has been noted 
on the Seikan Tunnel project (item 11, Table 2.1) but details on this work 
are not available. 

Continuous core drilling is a strong "next generation" 
horizontal drilling candidate where core sampling is required along the 
entire length of the hole. 

6.2 Chip Removal 

Reference has been made previously to the importance of 
removing the rock debris or "chips" created by the material disengage- 
ment technique. Chip removal is accomplished by the use of a flushing 
fluid. The fluid may be air, water, or drilling "mud'.' Drilling mud is 
typically a colloidal suspension of bentonite in water combined to form a 
thixotropic fluid. Other additives may be included in the mud to achieve 
a particular set of properties. 

In drilling a hole, the ideal fluid velocity is that velocity 
which is sufficient to pick up and carry away the largest particles 
created in the drilling operation, at the rate at which they are created. 



6-48 



INSTRING 
CATCHER 
(MOUNTED BELOW- 
FIRST JOINT OF 
DRILL PIPE). 



CORE BREAKER 

FOR PUMPING CORES 

TO SURFACE WITH 

UNINTERRUPTED 

DRILLING 




3' CORE BARREL 
FOR PUMPING 
3' CORE INTO 
INSTRING CATCH- 
ER UNDER SWIVEL 







Figure 6. 23 - Continuous Core Drilling 
(Courtesy, Drilco Industrial Operations) 



6-49 



MUD PUMP 




FINES DOWN TO 1200 MESH 
TO BE REMIXED WITH SCREENED - 
MATERIAL FOR TOTAl SAMPLE 



HAMMER SUB 

RETURNING SAMPLES FROM 

AIR OR LIQUID HAMMER TO 

SURFACE THROUGH INNER TUBE 



Figure 6. 24 - Continuous Cuttings Sampling 
(Courtesy, Drilco Industrial Operations) 



6-50 



Lower velocities will leave chips in the hole where they will be further 
broken up by the drilling operation, wasting energy and slowing the bit 
penetration rate. Velocities higher than necessary may errode the sides 
of the hole, leading to hole stability problems. 

A secondary function of the drilling fluid is to act as a 
bit coolant and lubricant. The cooling function is particularly im- 
portant in diamond drilling where the interruption of fluid flow can lead 
to a "burnt" bit. Drilling mud is the best lubricant among the drilling 
fluids and materials are sometimes added to the drilling mud to further 
enhance its lubricating properties. 

The generally accepted level of air velocity adequate for 
chip removal in a vertical hole is 3,000 ft/min (15.24 m/sec). ' 

When drilling with water or mud, the accepted optimum velocity is 

21 27 
120 ft/min (0.61 m/sec). ' A number of correlations for the minimum 

fluid velocity required for the horizontal transport of solids are available 
in the literature. These correlations are of an empirical or semi- 
theoretical nature. In general their use requires detailed information 
about the drilling - penetration rates, density of solids, chip size and 
size distribution, etc. they are complicated to calculate, and are pre- 
dominantly for the transport of uniformly sized solids in smooth, round, 
non- rotating pipes. Even with these restrictions imposed, one finds 
variations of more than an order of magnitude in the predicted minimum 
transport velocity. The minimum velocities predicted for horizontal 
transport do tend to be higher than the velocities predicted for vertical 
transport. 

There is very little data from which to develop fluid 
velocity rates for horizontal drilling. There are certainly no "accepted 
optimum velocities" as there are in vertical drilling. Based upon the 
experience of Jacobs Associates in pneumatic horizontal drilling, 
Williamson concluded that the optimum velocity for flushing horizontal 
holes with air is 7,000 ft/min (35.6 m/sec). 10 In horizontal coal drilling 
with water, Fenix and Scisson noted that, with a fluid volume flow rate 



6-51 



of 25 gpm, "penetration rate was nearly maximum and hole cleaning was 
good." This corresponds to a flow velocity of 145 ft/min. (0.74 m/sec) 
for the equipment used in this work. Based on the information available, 
the figure of 7,000 ft/min (3 5.6 m/sec) for air flushing and 150 ft/min. 
(0.76 m/sec) for liquid flushing represent a starting point from which to 
determine the equipment required for chip removal. 

Once a flushing medium has been chosen, and the hole 
diameter and length and drill string size have been selected, the rule 
of thumb flushing velocity can be used to estimate volume flow rate 
and pressure drop. From these estimates, equipment can be selected. 

The following sections present criteria for the selection of 
the flushing medium and estimates of required volume flow rates and 
pressure drops for pneumatic and hydraulic flushing of horizontal holes. 

6.2.1 Selection of a Flushing Fluid 

Selection of the flushing fluid is the first step in 
determining equipment requirements for chip removal in horizontal 
drilling. This section presents general considerations as well as current 
practice and specific recommendations for each of the four candidate 
drilling techniques. 



Of the three flushing fluids under consideration, 

air is generally termed the best scavanger, water the best coolant, and 

21 
mud the best lubricant. However, there are other factors which can 

dictate the choice of a flushing medium. If there is a water shortage 

in the drilling area, air flushing may be the only alternative available. 

On the other hand, when drilling below the water table or in any situation 

where water inflow is encountered, water or mud may have to be used. 






6-52 



In petroleum drilling and some deep diamond drilling, 
drilling mud is the preferred drilling fluid for several reasons. Some of 
the most significant are; (a) the ability of mud to seal "lost circulation" 
zones, (b) the lubricating properties of mud with respect to increasing 
bit performance and reducing friction between the drill string and hole 
wall, (c) the thixotropic nature of mud which keeps the chips in suspension 
and prevents them from settling to the bottom of the hole when drilling is 
interrupted, and (d) the ability of mud to prevent collapse of the hole. 
(Control hole stabilization) Items (a), (b), and (d) are significant in 
horizontal drilling, but item (c) is not particularly important. The 
application of drilling mud to hole stabilization problems is discussed 
in detail in Section 6.3, while the frequently related problem of lost 
circulation is covered in Section 6.2.3. In general, the need for control 
of lost circulation, hole stabilization, and lubrication of the drill pipe to 
hole interface favor the use of water or drilling mud as a flushing fluid 
in long horizontal drilling. Current practices and specific recommendations 
for each of the candidate drilling techniques are discussed in the following 
paragraphs. 

Diamond core drilling conducted in competent rock 
has usually been conducted using water as the flushing medium. (Items 
2,3,4, and 5, Table 2.i) In cases where lost circulation and hole stability 
problems have been encountered, drilling mud has been used. (Items 6 
and 11, Table 1.1) These procedures represent logical recommendations 
for horizontal drilling with diamond wireline equipment. 

In horizontal rotary drilling the Japanese have used 
drilling mud for drilling in the soft, broken materials encountered in the 
Seikan Tunnel work. (Items 1 and 12, Table 1.1) Horizontal rotary 
drilling in this country has been conducted using water as the flushing 
fluid. (Items 14, 15, 17, Table 1.1) Generally the flushing fluid recom- 
mendation for horizontal drilling are the same as for wireline core drilling, 
water should be satisfactory when drilling competent rock if no circulation 
problems are encountered, and drilling mud is recommended to control 
lost circulation and hole stability problems. 



6-53 



The recommended chip removal procedures for down- 
hole motor drilling are the same as those recommended for diamond 
wireline core drilling and rotary drilling. It is particularly important 
to minimize the free solids content in the drilling fluid when drilling 

with fluid powered downhole motors. Dyna-Drill recommends that sand 

22 
content be held to an absolute minimum with less than 1% recommended. 

Sand accelerates bearing and motor element wear in fluid driven down- 
hole motors. 

Pneumatic flushing must be used with down hole 
percussive drilling. Water injection into the air flushing stream may be 
employed to enable percussive drilling to be utilized in slightly wet or 
"sticky" formations. One part of water per 1,000 parts of free air is 
used. The requirement that air flushing be used with percussive 

drilling limits the application of this technique to competent rock. 

6.2.2 Hydraulic Chip Removal 

As indicated earlier, the recommended velocity for 
hydraulic flushing of horizontal holes is 150 ft/min. (0.61 m/sec.) The 
left hand vertical axis of Figure 6.2 5 gives liquid flow rates in gallons 
per minute (GPM) for various hole diameters and standard drill rod 
sizes. Figure 6.26 gives estimated pressure drops for different 
hole diameters and drill rod sizes. These pressure drop estimates 
were arrived at by assuming a friction factor, f, of 0.005. 

Liquid volume flow rates are obtained from Figure 
6.25 by entering the horizontal axis at the value for the hole diameter. 
This point is followed vertically to the appropriate line for drill rod size 
and then horizontally to the left hand vertical axis where the flow rate 
in GPM is obtained. For example, a 5" (127 mm) diameter hole with NW drill 
rod will require approximately 111 GPM (420 LPM of water or mud. Estimated 
pressure drops are obtained in a similar fashion from Figure 6.26. The 
right hand side of the horizontal axis is entered at the appropriate drill 
rod size. This point is followed vertically to the correct hole diameter 



6-54 



EW 



1300 




3 (76) 4 (102) 5 (127) 6 (152) 

Hole Diameter, inches (mm) 

Figure 6. 25 - Flushing Fluid Flow Rate Versus Hole Diameter For 
Various Drill Rod Sizes 



6-55 




CO 


2 






o 
o 


.S 


in 


o 




•H 




43 




^ 




8 




a 1 




(0 






O 


m 


00 


0) 

ft 


sd 










CO 


o 


£ 


o 


i—i 


o 


A4J 2 


I - 1 




o +» -r i 




° 2 "3 




QhaJ 




3 m 




<u <0 TJ 




n ii >> 




g*» 


^_> 


to 


CO 


(1) ,— — - 




IhhN 


o 


ft — 


w 




o 




o 




in 





ft 
o 

P 

3 



6-56 



line. This point is followed horizontally until it intersects the appropriate 
hole length line. The abscissa of this point gives the estimated pressure 
drop. For example, NW drill rod in a 5" (127 mm) diameter, 10,000' 
(3048 m) hole gives a pressure drop of approximately 614 psi (4.23 x 10 N /m ), 

6.2.3 Pneumatic Chip Removal 

As indicated previously, the recommended velocity 

for pneumatic flushing of horizontal holes is 7,000 ft/min (15.24 m/sec). 

The right hand vertical axis of Figure 6.2 5 gives air flow rates in cubic 

feet per minute (CFM) for various hole diameters and drill rod sizes. 

Estimated pressure drops as a function of hole diameter, hole length 

and drill rod size are given in Figure 6.26. This figure assumes a 

uniform friction factor and air density throughout the entire pipe length. 

The effect of air density changes can be easily introduced but, owing to 

the other approximations involved, was not included. The use of 

Figures 6.25 and 6.26 is described in Section 6.2.2. For example 

pneumatic flushing of a 5" (127 mm) hole, 10,000' (3048 m) long, with NW 

3 
drill rod will require approximately 710 CFM (20 m /min) and have an 

estimated pressure drop of 1500 psi (10.34 x 10 N /m ). 

6.2.4 Lost Circulation 

Lost circulation occurs when the drilling fluid flows 
into the formation being drilled rather than returning to the surface with 
its load of debris. In some rare instances lost circulation can be 
tolerated but this is not usually the case for several reasons. When 
drilling is interrupted the debris which have been carried back into the 
formation can return and clog the hole. A second consideration is the 
cost of the drilling fluid. In arid regions water may have to be trans- 
ported to the drill site and lost circulation places an increased burden 
on water transportation requirements. When drilling mud is used mud 
costs are a significant part of the hole cost, so the mud must be re- 
covered and recycled. Lost circulation can be caused by porous 
formations, faulted or broken formations, or any other formation character- 
istic which provides an alternative flow path for the drilling fluid. The 



6-57 



pressure of the drilling fluid itself may cause formation faults or "blow 
outs" which allow the fluid to escape. 

There are three methods for controlling lost cir- 
culation, in order of preference; (a) the use of drilling mud and drilling 
mud additives, (b) grouting, and (c) casing of the hole. When air 
flushing is employed, alternative (a) is eliminated. In the single 
documented case of long horizontal drilling with pneumatic flushing, 
lost circulation was cured by pumping slugs of very wet sand -cement 
grout into the hole, alternating with slugs of water. Drilling mud 

controls lost circulation by forming a cake on the hole wall. The cake 
is formed when some of the mud liquid phase flows into the formation, 
allowing the solids phase to form a coating on the hole wall. This 
solids coating prevents further liquid loss to the formation. When 
formation faults are coarser, and the caking mechanism is no longer 
effective, bran, sawdust, rice hulls, walnut shells, or proprietary 
preparations, available from drilling mud companies, may be added to 
the drilling mud in an attempt to block lost circulation paths. The next 
step to be employed would be an additive which is pumped into the 
formation and allowed to gel. From here, the next step is cementing 
or grouting in which the lost circulation zone is isolated with packing 
devices and cement or grout is pumped into the zone. After the 
material hardens, drilling is resumed. Should the preceeding techniques 
all prove ineffective, the hole must be cased to seal the lost circulation 
zone. 

The subjects of drilling mud and grouting can 
become quite complex. Within the drilling industry, application of 
these techniques is handled by service companies when the expertise 
required is beyond the capabilities of the drilling contractor. Material 
suppliers and service companies are listed in Appendix A. 

6. 3 Hole Stabilization 

In an ideal situation, the horizontal drilling operation would 
be conducted in competent rock and no special steps would be required to 



6-58 



stabilize the hole. This is likely to be the case for a substantial percent- 
age of ho rizontal drilling in rock. When hole stability problems are en- 
countered during the drilling operation, the steps which can be taken to 
solve the problem are, in order of preference: 

(1) Use of drilling mud. 

(2) Grouting. 

(3) Casing. 

Note that these are the same steps discussed in Section 6.2.4 in 
connection with lost circulation problems. 

If a borehole is to be used for geophysical experiments, 
the hole may have to remain open for up to one year after drilling is 
completed. Drilling mud contributes to hole stability only during 
drilling operations. Therefore, grouting and casing are the only techniques 
available to ensure long term hole stability. Sensing requirements can 
prohibit the use of metallic casing. (See Section 5.1) The procedures 
followed for each of the three techniques are as follows: 

(1) Drilling mud aids hole stabilization in much the same 

manner as it controls minor circulation loss. The 
drilling mud forms a cake on the hole wall and the pressure 
across the cake stabilizes the hole walls and prevents their 
collapse. In vertical drilling the required pressure 
differential is provided by the hydrostatic head of the drilling 
mud column. In horizontal drilling a packing gland must 
be used to seal the drill string so that pressure can be 
applied to the mud column. This technique is illustrated 
in the discussion of the operating procedures to be followed 
with various drilling techniques in Section 6.1. As noted 
above drilling mud does not affect hole stabilization after 
the drilling operation is completed. Cementing, grouting, 



6-59 



DRILL ROD EXPENDABLE BIT 



Horizontal hole is drilled by conventional rotary method. The Aardvark offers a wide range 
of height and angle positioning. 



SLOTTED PVC SCREEN DRILL ROD BIT 

I I 1 



Upon completion of the boring, P.V.C. well screens are inserted inside the drill rod to the 
full length of the hole. 



FLOATING LOCKING PISTON DRILL ROD SCREEN BIT 

/ — J I— I 



Floating locking piston is inserted, holding the screens in place by hydraulic pressure 
while the drill rod is withdrawn. 



SLOTTED PVC SCREEN 



BIT 

I 



Completed drain installation. Screens of fine slot size prevent clogging and formational 
mining. Collector lines or ditches can be installed. 



Figure 6. 27 - Installation Procedure for Horizontal Drainage Screens 
(Courtesy, Tigre Tierra, Inc. ) 



6-60 



or casing is required to ensure long term stability. A 
recent survey of drilling mud technology is provided in 
Reference 3 7. 

(2) Grouting is used where drilling mud cannot control 

hole stability problems and where stability is required 
for a period of time after drilling is completed. 
Grouting is conducted by withdrawing the drill string, 
inserting a packer, and injecting the grout into the 
unconsolidated zone. After the material hardens, it 
is drilled through and the operation continues. In 
some cases the grout may be injected through the 
drill string without recourse to a packer. If collapse 
of the hole wall is triggered by ground water, drilling 
may be continued while the ground water flow is con- 
trolled with the packing gland or water flow can be 
stopped with the packing gland and grouting conducted. 
Appendix C contains a more comprehensive presen- 
tation of grouting technology. 

(3) Steel is the only successful casing material developed to 

date despite extensive development efforts in fiber reinforced 
plastic casing. 27 Normal practice would be to case a hole 
when the techniques discussed above are not successful or 
when long term hole stability is required. Essentially all 
the holes drilled in the petroleum industry are cased. 

Hole stability problems have been the most significant 
problem encountered in long horizontal holes on the Seikan Tunnel project. 23 
All of the techniques described above have been successfully applied to 
solving hole stability problems on the Seikan project. 5,23,24,28 

Soil Sampling Services of Puyallup, Washington, has de- • 
veloped a technique for placing horizontal drains which may have appli- 
cation as a "next generation" casing technique. This technique is 



illustrated in Figure 6.27. In a casing application, the PVC pipe would 
not be slotted as it is when used as a well screen. Since the pipe is 
inserted inside of the drill pipe it does not have to be driven as normal 
casing would. However, the fact the pipe must fit inside of the drill 
string results in a considerable loss in hole diameter. This technique 
shows promise as a "last resort" non-metallic casing method of insuring 
hole stability. 

6.4 Borehole Guidance 

As discussed in Section 5, borehole guidance involves two 
distinct operations, (1) survey of the borehole to determine its attitude 
and position and thus determine the deviation of the hole from the desired 
trajectory, and (2) steering of the drilling system, first to limit deviation 
from the desired trajectory and second to correct deviations and direct 
the hole to the desired trajectory. The goal of this study is to keep 
maximum hole deviation to 30 feet (9.14 m) over the entire hole length. 

Borehole survey and the steering actions are distinct 
operations. However, the functions are often confused as the steering 
is dependent upon the results of the survey. This has led to quoted 
results of guided drilling accuracies which are often misleading. The 
survey provides the reference standard against which drilling and steering 
accuracy is measured. Thus steering accuracy is represented as the 
ability to direct the borehole along a trajectory indicated by the survey 
system. The survey system has random errors and cumulative bias 
errors. However, the opportunity to check the accuracy of the basic 
survey by external calibration usually does not exist. Thus, the true 
drilling errors are the vector sum of both the survey and the steering 
contributions, but only the steering portion of this sum can be reported. 

6.4.1 Factors Affecting Hole Trajectory 



6-62 



6.4.1.1 Gravitational Effects 

In horizontal drilling, gravitational effects 
would normally tend to make the drilling assembly move in a downward 
arc from its intended horizontal course. However, with the proper 
drill string configuration, it is possible to use gravitation forces to 
cause the drill assembly to steer up or down from a horizontal trajectory. 
These procedures are discussed in Section 6.4.2. 

6.4.1.2 Rock Hardness 



Some studies have noted that as rock 
hardness increases, problems of directional control intensify. Case 
histories appear to support this assumption. In horizontal drilling in 

soft materials effective directional control has been achieved by varying 

1129 
drill string configuration and drilling parameters ' while in horizontal 

drilling in medium to hard rock, hole correction with wedges has some- 

14 
times been required at 10 foot intervals. 



6.4.1.3 Formation Effects 

There are a number of theories which 
seek to offer explanations of the effect of formation characteristics on 

hole deviation. None of these theories is rigorous and none seems to 
apply in all cases. John Melaugh reviews several of these theories in 
his paper titled, "Directional Drilling: A Survey of the Art and the 
Science]' A portion of that discussion is reproduced here. 

"The anisotropic formation theory assumes formations to possess 
different drillability parallel and normal to the bedding planes with the 
result that the bit does not drill in the direction of the resultant force. 
Each formation is characterized by its dip angle and an empirical 
constant anisotropic index. 



6-63 



The formation drillability theory seeks to explain deviation angle 
change as a result of the difference in drilling rates in hard and soft 
formations where the drill bit is not normal to the formation plane. 
The bit drills slower in that part of the hole in the hard formation 
(Figure 6.28). 

The drill collar moment theory proposes that the weight on bit 
causes a moment when drilling from one formation to another of 
different hardnesses because the harder formation takes more of the 
weight (Figure 6.29). The side forces present at the bit are different 
depending on whether progress is from hard to soft or soft to hard. 

The miniature whipstock theory is based on the tendency of 
relatively brittle formations to fracture perpendicular to the bedding 
plane (Figure 6.30). If these fractures occur in real formations 
and if such whipstocks are created, this could explain the generally 
accepted idea that the bit turns up dip. 

Another whipstock theory, exemplified in S. R. Knapp's papers, 

could be considered to conflict with the foregoing miniature whipstock 

31 

theory. This theory is based on a bit's ability to cut sideways with a 

reaming action when unbalanced side forces exist due to crossing a 

bedding plane (Figure 6.31 ). This theory is also said to apply to 

steeply dipping formations. Another idea that has been generally accepted 

in the past is that in steeply inclined formations the bit tends to turn 
and follow the bedding planes (Figure 6.32)1' 

Other references support the general 
conclusions that: 

(1) The drilling assembly will tend to drill perpendicular to 

the formation bedding planes when the planes are inter- 
sected at an angle greater than 45°. ' ' 



6-64 



SOFT 
ROCK 



HARft 



/?OCX , v_£.. 



m 



HARD+ 

/?6ck% 




SOFT 
ROCK 



DEFLECTS UPDIP DEFLECTS DOWN DIP 



Figure 6. 28 - Formation Drillability Theory of Hole Deviation 



HARD 




Figure 6. 29 - Drill Collar Moment in Drilling Dipping Formations 



6-65 




Figure 6. 30 - Tendency of Bit to Drill Perpendicular to 
Moderately Inclined Bedding Plane 



UPD/PHERE 



DROP ANGLE HEFE-+?. 




DOWN D/P HERE 



Figure 6. 31 - Whip^tock Effect Caused by 
Change in Formation Hardness in 
Steeply Dipping Beds 



6-66 



(2) The drilling assembly will tend to drill parallel to the 

formation bedding planes when the planes are intersected 

1 1 "^7 
at an angle less than 45 . ' 

6.4.1.4 Drilling Torque 

The direction of rotation of the bit and 

drill string is clockwise. It is generally accepted that this creates a 

29 
tendancy for horizontal holes to drift to the right. A review of the 

hole data on AEC horizontal drilling in Table 6.8 (see p. 6- 113) supports 

the right hand drift theory. 

6.4.2 Guidance Procedures 



6.4.2.1 Survey 



The survey of the hole is such a special- 
ized process that it is normally accomplished by a service company. 
However, some drilling contractors have obtained and modified their own 
tools for horizontal drilling. 

The exact methods of survey and compu- 
tation depend upon the design of the particular tool, and the preferred 
computational techniques of the individual service companies. However, 
they all are derivable from a common vector approach. Essentially, 
they are three-dimensional derivations of chain and compass sur- 
veying. 

As the hole is drilled, the bearing with 
respect to North, and the elevation angle with respect to the vertical 
are measured at discrete intervals. The locations of these measure- 
ments are referred to as stations. The hole between stations is assumed 
to be represented by a line vector, the length of which is also measured. 



67 




Figure 6. 32 - Tendency of Bit to Follow Bedding Plans 
Intercepted at a High Angle 



6-68 



These three measured quantities are sufficient to locate the surveyed 
station, with respect to the last station previously surveyed. It should 
be emphasized that this is only a relative, incremental measurement. 
The true location of the hole is obtained by carrying this survey, plus 
any new incremental changes from station to station thus any bias errors 
are cumulative and any random errors add as the square root of the sum 
of the squares (rms value). 

There are only two types of tools for in- 
hole surveys generally in use today, the magnetic single- shot and the 
magnetic multi- shot. In-hole steering tools which rely on either gyro- 
scopic or magnetic principles, or a combination of both are either 
available on a custom design basis, or are expected to be available as 
a service in the near future. 

Single- shot and multi- shot equipment really 
differ but little. A single- shot takes only a single survey point each time 
it is used. A timer is set on the surface to allow sufficient time for 
the instrument to come to rest. The timer turns on a light and takes a 
picture of a two-dimensional compass card, and the instrument is with- 
drawn. A multi- shot uses a film strip and sequential timer which takes 
a picture at equal increments of time. The timer simply turns on the 
light, takes the picture, and advances the film strip. The time increment 
can be set to take a picture as frequently as every few seconds or to 
almost any extended increment. 

The single shot is normally owned or 
rented by the drilling contractor. It is usually operated by a directional 
drilling specialist on the drilling crew. 

Standard practice for precision surveys is 
to take a single shot survey every 30 feet (9 m). This is a convenient 
length, since 30 feet (9 m) is the standard single section length of drill 
pipe in vertical drilling. Horizontal drilling normally uses 10 or 20 foot 
(3 or 6m) sections. Thus a survey point would be taken every length, or 
every other length of drill rod. 



6-69 



Magnetic survey instruments must be 
isolated from the influence of the drill string if they are to give accurate 
results. It is common practice to use non-magnetic drill collars in the 
drill string around the point where the in- hole survey tool will rest. 
There are charts available for slant hole directional drilling to define 
the length of drill collar required to reduce the survey error below 
specified amounts. Figure 6.33 is one such chart. It can be extrapolated 
that if the hole is horizontal (90°), even the longest drill collars listed 
are not recommended beyond 30 degrees east or west of north or south. 

The normal procedure is to pump the 
survey instrument down the center of the drill rod. This is also known 
as "go- deviling'.' The package has non-magnetic extension rods attached 
so that it will be properly located within the drill string with respect to 
the non-magnetic drill collars behind the bit. Normally, there is a mule 
shoe sub in the drill string which orients the survey tool through cam 
alignment at the bottom of the hole. 

The timer on the single shot is set to 
allow sufficient time for the tool to be go- deviled down the string at 
fluid velocity and come to rest. The picture is taken and drilling 
continues. When it is time to add a new length of drill rod, the single 
shot is retrieved by a wire line. The drill string is broken to add the 
new section and the single shot is retrieved. The directional driller 
disassembles the package, removes the film, reloads and resets the 
timer. The tool is then reassembled, and inserted in the drill string 
and the process is repeated. 

With wireline core drilling equipment, 
the drill string is withdrawn from the hole bottom approximately 20 
feet (6. 1 m) and the survey instrument, in the instrument barrel with 
15 feet (4. 7 m) of non-magnetic spacer bars behind, is pumped down 
through the core barrel and bit. No mule shoe device is used to 
orient the instrument. In this case the instrument is retrieved before 
drilling resumes. 



.-70 




14/14 FREE MONEL 




14/21 FREE MONEL 




Approximate Compass Error 
Due to: 

1. Drill stem pole strengths of 3000 ± EMU above 
monel and 500 - EMU below monel and 250 - 



EMU between tandem collars. 



NOTE: 



These are assumed values arrived at from 
various field tests. 



2. Compass position 1/2 up from the bottom of 
the free monel of the bottom collar. 

3. Earth's horizontal intensity of: .26. 



NOTE: These curves are intended only as a guide 
in the selection of the proper K-Monel 
collar. The compass errors are 
theoretically true for the above conditions 
but are NOT to be used to correct records 
taken in the hole, as the pole strength 
will vary in an unpredictable fashion. 

NOTE: Numbers on axis indicate lengths of 
paired tandem collars. 



21/21 FREE MONEL 




14/25 FREE MONEL 




21/25 FREE MONEL 



Figure 6.33. Guide for Selecting Non-Magnetic Drill Collars 

6-71 



The film is developed and read. Each 
manufacturer has specialized equipment to enable the driller to read the 
film, only three pieces of data are common to all. The azimuth angle 
is read with respect to magnetic north. The elevation angle is read 
with respect to the lccal vertical, and the orientation of the muleshoe 
sub with respect to either the high or low side of the hole. A fourth 
piece of data, the survey depth, is taken from either an odometer on 
the wireline, or from the drillers records of the lengths of drill rod in 
the hole. All the information necessary for survey, navigation or steering 
can be derived from these four quantities. 

The survey technique involves standard 
chain and compass procedures. Figure 6.34 shows the geometry involved. 
Let: 

= The Azimuth, Degrees from North 

6 = The Elevation Angle, Degrees from Vertical 

L. = The cable length, feet 

X = The North Component, Feet 

Y = The East Component, Feet 

Z = The vertical component, Feet 



n = The number of survey points. 

& ( ) = The change in any of the above from the previous (n- 1th) 
reading. 

From the geometry in Figure 6.34 it can be derived that: 

AZ n = AL n COS 6 

AX = AL sin cos 

n n r 



6-72 







Figure 6. 34 - Survey Coordinate Systems 



6-73 



AY = AL sin 6 sin 
n n 



n 



Z 



I AZ n 



X= V AX n 



= I 



AY 
n 



Note 9 and are true angles corrected for both magnetic declination and 
deviation errors. The values of X, Y, and Z are in the form necessary 
to make direct progress plots of both plan and elevation view of the hole. 

The actual summations can be either 
numerical or graphical. The progress of the hole as surveyed is 
normally plotted against the projected plan and elevation view of the 
drilling plan. This provides the driller with the information necessary 
to determine the needed corrections. 

Survey calculations can easily be com- 
puterized. In programming the computation, it is assumed that changes 
in bearing and inclination are uniform between survey stations, and 
changes are distributed over the survey increment. 



6.4.2.2 Stee 



ring 



The first step in steering is to attempt to 
minimize drilling assembly deviations. The ability of the drilling assembly 
to resist factors which cause deviations (see Section 6.4.1) is proportional 
-to the stiffness of the drilling assembly. In petroleum drilling, stabilizers, 
collars, and reamers are used to stiffen bottom-hole drill assemblies. 
(See Figure 6. 3 5) 



6-74 






Stabilizers are usually placed immediately 
behind the bit and at intervals along the drill string. Since stabilizers 
have an outside diameter only slightly smaller than the hole diameter, 
they serve to center the drill string and minimize whipping or bending. 

The function of drill collars in providing 
weight to the bit in vertical and directional drilling has been discussed 
previously. Being heavy and of a diameter only slightly smaller than 
the hole, drill collars are also very rigid. Square drill collars go one 
step further in that they are comparable to drill collars with full length 
stabilizers. 

Reamers are sometimes placed behind the 
bit to keep proper hole gage. Reamers may have rolling cutter blades or 
diamond studded blades. They also serve to center the drill string and 
minimize whipping and bending, in much the same manner as stabilizers. 

Figure 6.3 5 illustrates (a) stationary and (b) 
blade type stabilizers. A normal length of drill pipe (c) is illustrated 
along with round (d) and square (e) drill collars. A roller reamer is 
also illustrated (f). Figures 6.36 thru 6.38 illustrate the procedures 
followed in employing stabilizers, collars, and reamers to stiffen bottom 
hole assemblies. 

Documentation on the use of stabilization 
techniques in horizontal drilling is very limited. Fenix and Scisson noted 
success in limiting hole deviation through the use of stabilization procedures 
in horizontal drilling in coal. An assembly utilizing a stabilizer immediately 
behind the bit, a 20 ft (6.1 m) collar, and a 2nd stabilizer gave minimal 
lateral deviation and allowed vertical deviation to be controlled by varying 
thrust and rpm. 

This latter point brings up the "art" facet 
of the steering procedures. "Drilling technique, one of the most important 
means of preventing deviation, is hard to define as it is an art depending 



6-75 





5 d 

o S 

u 



6-76 




STIFF BOTTOM HOLE ASSEMBLIES 



2nd Stabilizer 
Helps 



Stabilizer Here 
t Essential — 

Rubber Sleeve 
Type Preferred 

Rotating Blade 
Type Acceptable 




Examples: 
73/4" dia. i 
8%" hole 

10" or 11" i 
121/4" hole 



3 Point Reamer 
"Q" or 
Knobby®Rolling 
Cutters 



HARD FORMATIONS 

The assembly at left 
will: 

1. Assure a full gage 
hole with no reaming 
back to bottom. 

2. 1 ncrease bit life 
through improved sta- 
bilization. 

3. Further increase pen- 
etration rates because 
optimum weights are 
higher on stabilized 
bits. 

4. Reduce offsets and 
spiralling in hole. 

5. Limit sudden hole 
angle changes and dog- 
legs. 

6. Moderately resist 
hole angle build-up. 



MAINTENANCE TIPS 

1. Keep bottom reamer 
in good shape, near 
hole size. See pages 
41-44 

2. Use the Knobbyf 
tungsten carbide insert, 
cutter for abrasive for- 
mations. 

3. Keeping stabilizer at 
30' level near hole 
size increases its ef- 
fectiveness. 

4. Excessively rapid 

wear on Rotating Blade 
Stabilizers may be over- 
come by using Rubber 
Sleeve Type. 

FOR HARD FORMATIONS 



SOFT FORMATIONS 

The assembly at right 
will: 

1. Increase bit life 
through improved sta- 
bilization. 

2. Further increase pen- 
etration rates because 
optimum weights are 
higher on stabilized 
bits. 

3. Reduce offsets and 
spiralling in hole. 

4. Limit sudden hole 
angle changes and dog- 
legs. 

5. Moderately resist 
hole angle build-up. 

6. Reduce pressure-dif- 
ferential sticking ten- 
dencies of this section 
of assembly. 



MAINTENANCE TIPS 



1. Suggest maximum 
permissible wear on 
bit stabilizer be about 
1/8" on diameter. The 
tungsten carbide insert 
Rotating Blade stabiliz- 
er is specially recom- 
mended at bit. 

2. Limit wear on stabi- 
lizer above 30' level to 
about 1/4". 



Note: Use rotating blade 
stabilizers in "non- 
abrasive" formations. 



Rotating Blade y 
Stabilizer 
Essential 



30' Drill Collar 

Large Size 

Essential 



Rotating Blade 
Stabilizer 
Essential 



30' Drill Collar 
Large Size' 
Essential 

Examples: 

8" dia. in 

W hole 

9" or 10" in 

121/4" hole 

Rotating Blade 

Stabilizer — 

(Must have 

large contact 

area with hole 

wall) Keep it 

as close to bit 

gage size as 

possible. 



FOR SOFTER FORMATIONS 



Figure 6.36 - Stiff Bottom - Hole Assemblies (Courtesy, 
Drilco Division of Smith International, Inc.) 



6-77 



no 



STIFFER BOTTOM 



HOLE ASSEMBLIES 



Stabilizer here 
'essential 
Rubber sleeve 
type preferred 
Rotating Blade 
type acceptable 



30 Foot long 
'Drill Collar 
large size 
essential 



Stabilizer here 
^essential 
Rubber sleeve 
type preferred 
Rotating Blade 
type acceptable 



8 to 12 Foot 
Long Drill 
Collar — Large 
Size Essential 



Examples: 
7%" dia. in 
8%" hole 
10" or 11" 
dia. in 12%" 
hole 



■6 Point 
Reamer "Q" 
or Knobby® 
Rolling Cutters 



HARD FORMATIONS 

1. Assure a full-gage 
hole with no reaming 
back to bottom. 

2. Increase bit life 
through improved sta- 
bilization. 

3. Further increase pen- 
etration rates because 
optimum bit weights 
go higher with more 
effective stabilization. 

4. Greatly reduce off- 
sets and spiralling in 
the hole. 

5. Greatly restrict sud- 
den hole angle changes 
and dog-legs. 

6. Restrict hole angle 
build-up. 



MAINTENANCE TIPS 

1. Keep bottom ream- 
er in good shape, near 
hole size. See pages 
41-44. 

2. The closer the sta- 
bilizers to bottom, the 
more essential it is to 
keep them near hole 
size. 

3. In abrasive forma- 
tions, a good combina- 
tion for the reamer is, 
Knobby® Cutters at bot- 
tom and "Q" cutters 
at top. 

4. Excessively rapid 
wear on Rotating Blade 
Stabilizers may be over- 
come by using Rub- 
ber Sleeve Type. 



SOFT FORMATIONS AND NON-ABRASIVE HARD FORMATIONS 



The "Drilco Full-Flo 3. Greatly reduce off- 
Assembly" at right sets and spiralling in 
will: hole. 



FOR HARD FORMATIONS 



1. Increase bit life' 
through improved sta- 
bilization. 

2. Further increase pen- 
etration rates because 
optimum bit weights 
go higher with more 
effective stabilization. 

MAINTENANCE TIPS 

1. Bottom square sta- 
bilizer section should 
be maintained very 
close to hole size. In 
some cases the tool is 
made with zero clear- 
ance and is allowed to 
wear only 1/16" on 
diameter. Somewhat 
more wear can be tol- 
erated in the larger 
hole sizes. 

2. Maintenance of low- 
est Rotating Blade Sta- 
bilizer is almost as crit- 
ical as for the Modified 
Short Square Drill Col- 
lar. 

3. Stabilizers higher up 
the hole may be al- 
lowed to wear some- 
what more, depending 
on distance from the 
bit. 

4. In 6y 2 " holes, 1/16" 
wear is twice as great, 
proportionately, as in 
12%" holes. 

5. Very close mainten- 
ance to gage is more 
expensive, but in crit- 
ical situations it is 
worth it. 

FOR SOFT FORMATIONS AND __ 
NON-ABRASIVE HARD FORMATIONS 



4. Greatly restrict sud- 
den hole angle changes 
and dog-legs. 

5.Greatly resist hole 
angle build-up. 



Another Stabi 
lizer at top of 
30' drill collar 
helps (essen- 
tial in larger 
hole sizes). 

30' Drill 
Collar" 
Large size 
preferred 



-m 



8 to 12 Foot 

Long Drill- 

Collar — Large 

Size Essential 



Rotating Blade 
Stabilizer 



Modified Short 

Square Drill' 

Collar 



Figure 6.37 - Stiff Bottom - Hole Assemblies (Continued) 



78 







SYIFFEST BOTTOM 



CONSOLIDATED FORMATIONS 



Another 

'stabilizer is 
recommended 
at top of this 
drill collar. 

30 Foot Long 
Drill Collar 
Large size 
' preferred. 

Use stabilizer 
here to in- 
crease length 
of assembly 
and to reduce 
wear at upper 
end of square 
drill collar. 

Rubber sleeve 
type best for 
abrasive 
formations. 
Rotating Blade 
type can be 
used in non- 
abrasive 
formations. 

.30 Foot 
Square Drill 
Collar 

Bottom Reamer 
recommended 
if formations 
are abrasive— 
if wear on 
Square Drill 
Collar is not 
excessive, it 
may be left 
off. 



Caution: This assembly 
must be reamed to bot- 
tom if part of the hole 
was drilled without a 
square collar. 



The Assembly at left 
will: 

1. Increase bit life 
through effective sta- 
bilization. 

2. Permit highest drill- 
ing rates because sta- 
bilization is maximum 
and optimum bit 
weights are highest. 

3. Provide maximum re- 
sistance to hole angle 
build-up. 

4. Provide maximum re- 
sistance to offsets and 
spiralling in the hole. 

5.Provide maximum re- 
sistance to sudden hole 
angle changes and dog- 
legs. 

MAINTENANCE TIPS 

1. If formations are 
abrasive and bits tend 
to drill under gage hole, 
be sure to use the ream- 
er and keep it out to bit 
diameter. This is best 
accomplished with a 
Drilco Knobby®Reamer. 

2. As with other "pack- 
ed hole tools", Square 
Drill Collars lose their 
effectiveness as wear 
progresses. Maximum 
permissible wear de- 
pends on how critical 
situation is. 

3. Rebuilding square 
drill collars should be 
done by controlled met- 
allurgical procedures. 
Drilco service shops are 
specially equipped and 
their people trained to 
rebuild square collars 
for maximum, trouble- 
free performance. 



Recommend/ 
large size 30' 

drill collar 

with stabilizer 

at top. 



HOLE ASSEMBLIES 



UNCONSOLIDATED FORMATIONS 



4. If you need some 
help on any of these 
procedures, contact 
your Drilco man. 
Where formations are 
such that the hole 
enlarges as it is 
drilled, wall support 
becomes intermittent, 
at best. To compensate 
for this a very long 
wall-contact assembly 
is recommended. The 
Tandem-Square Assem- 
bly lends itself well to 
this service because it 
has long wall contact 
surfaces. 

THE TANDEM SQUARE 
ASSEMBLY at right 
will: 

1. Provide all 5 of the 
benefits attributed to 
the regular square as- 
sembly on the opposite 
page. 

2. Make "Tattle Tale" 
technique feasible. 

Here's a technique 
some drillers have 
found useful in Air and 
Gas drilling. With this 
long rotating square 
assembly in the hole, 
any side force on the 
bit will cause a no- 
ticeable build-up in 
torque. Such side forces 
normally make the hole 
go crooked. 

Employing the Tattle 
Tale technique, the 
driller reduces weight 
when the torque goes 
up and thereby reduces 
the force tending to 
make the hole go 
crooked. This gives the 
driller a tool to con- 
trol deviation. 



Tandem 

Square Drill 

Collars 



This technique is parti- 
cularly effective when 
drilling with air. 

MAINTENANCE TIPS 

The recommendations 
for single squares also 
applies to tandem 
squares. 



Ordinary 
Reamer not 
required 
because un- 
consolidated 
formations 
rarely cause 
bits to drill 
under-gage 
hole. 




Figure 6.38 - Stiff Bottom - Hole Assemblies (Continued) 



6-79 



on the driller's "feel" for what is happening down the drill hole. This 
art, acquired only through experience, accounts for such variables as the 

Q 

proper control of bit pressure, rotary speed, pumping pressure, etc." 
The art aspect of deviation control can be minimized through wider use of 
instrumentation and subsequent documentation of drilling parameters. 

Drilling "by the numbers" has been successfully employed as a technique 

14 
for training inexperienced drillers. However, this approach does not 

have much support from the drillers themselves, and the practice is not 

widely employed. Consequently, no drilling parameter data base exists 

for horizontal drilling. 

When the driller establishes that a pattern of 
hole deviation is developing he must make a correction. This is accom- 
plished by making the hole deviate at an angle which will tend to bring the 
trajectory of the hole back onto the proper projected path called for in the 
drilling plan. 



The procedure of controlling vertical hole 
deflection by the use of a fulcrum effect has been applied in horizontal 
drilling in coal and the AEC horizontal drilling program conducted at 
Mercury, Nevada. Figure 6.39 presents the principles involved, A 
stabilizer, a few tens of thousandths of an inch smaller than the hole 
diameter is placed on the drill string near the bit. This acts as a 
fulcrum to balance the forces involved. The weight of the bit is 
balanced against the weight of the drill string suspended by the stabilizer. 
For any drill rod configuration, the rod creates a lever arm, which is 
constant depending on the weight per foot of the rod and its flexibility. 
Far removed from the stabilizer, the rod will lie on the bottom of the 
hole. Thus, there is only a relatively short section of rod to actually 
contribute the balancing force. This is shown in Figure 639 a. Figure 
6.39b shows the drill rod configuration used to cause the hole to climb. 
The stabilizer is placed close to the bit. The net downward force due 
to gravity is thus behind the stabilizer and produces an upward force on 
the bit. The force can be amplified by replacing the standard flexible 



6-80 



rod with a heavy drill collar. This not only adds weight because of the 
increased mass, but also adds force amplification due to the increased 
lever arm from the more rigid collar. This is illustrated in Figure 
6.39 c which shows this configuration. To make the hole fall, the 
stabilizer is moved back from the bit and the heavy collar now adds its 
weight to the bit and overbalances the suspended drill rod behind the 
stabilizer. 

Control of thrust and rpm are also used. 
The drilling contractor at the Nevada Test Site of the AEC has employed 
a system quite similar to the one in Figure 6.3 9 except that the 
stabilizer location is not changed. The configuration of Figure 6.3 9b 
is used to cause the resultant hole to climb. To cause the resultant 
hole to fall, the standard stabilizer is replaced with a diamond en- 
crusted stabilizer which thus becomes a reamer. With these config- 
urations, it has been found that upward deflection is increased with 
increased thrust and standard rpm's, while the hole can be made to 
drop with the diamond stabilizer, at increased rpm's and reduced thrust. 

Rommel and Rives used a configuration 
similar to Figure 6.39 and found that thrust and rpms became important 
control parameters. They did not indicate how it was applied. 

Logic would indicate that thrust and bit 
speed can be used to produce variations, primarily to amplify or reduce 
a tendency, wherein any particular drill string, and bit configuration in 
specific formation will climb or fall. There seem to be no hard and 
fast ground rules for their application. It is believed their effects will 
have to be learned empirically in each new hole and each new con- 
figuration. This merely reinforces the fact that much of the success 
of the operation will rest in the human factors of the drilling art. 

The fulcrum procedure has not been de- 
veloped as an effective steering technique in medium or hard rock. 



6-81 





4-> T3 






•H O +-> 






PQ OS -H 






pq 






m ih 






o rH m 






•H O 






+J ?H 






^Qt3 






60 rt 






•H T3 <D 


</> 




© C ^3 


0) 


Jh 


3E 05 < 


o 

5h 


0) 




o 


M 




Bin 


•H 






iH 




+-> 


• H 




• H 






PQ 


■M 




a 


C/} 




o 


4-> 




4-> 


e 




o 


O 




a> 


5-. 




1 


m 


Ph 




m 


U-r 


< 


1 


w 






H 




Jh 


O 




0) h3 m T3 


iH 




N (D O O 


3 




•H <P Pi 


Hh 




tH H -M 






• H O X i-H 


i 




,Q pu bOr-l 






rt Ph-h -h 


rt 




+-) 3 © 5-i 


CT> 




co co^ Q 


KJ 




A_ ^» 


vO 

a; 

3 








bo 





X 



Gravity 







O 








• H 








+-> 








CTJ 








5-i 








3 








bO 








• H 








m 








a 








o 








u 








bO 








a 








•H 








.0 








e 








■H 








rH 




r-H 




u 




rH 








•H 




1 


+J 


fH 






m 


Ti n 




X 


< 


<D 




en 




+-> m 




K) 


5-< 


5h O 






0) 


o 




vO 


N! 


Pw4-> 


bo 




•H 


"* X 


£ 


O 


rH 


, / b0-H 


5* 


•H 


tfl -H 


H 


3 


£i 


Pi <D 


+J 


bO 


aJ 


D & W 


• H 


+-> 






Hh 


CO 



Pi 

o 

bO 



6-82 



When the fulcrum procedure is not effective or when azimuthal corrections 
are required, a deflecting tool must be employed. 

The correction must be made in a different 
coordinate system than the survey coordinates. The driller simply 
determines how far the hole is to the left or right and above or below 
the planned course. The correction angle, \\j may be computed with 
respect to the high or the low side of the hole and is also shown on 
Figure 6.34. 

Let f = the vertical error 

e . = the azimuthal error 
A 

ip - the deflection angle 
Then for high side reference 

ip = tan" 1 ~ 
V 

e 



- 1 A 

= cot" -A for low side reference 



A deflecting tool is then used to deviate the hole at the angle ip, to the 
reference side of the hole. Deflecting tools apply a lateral force to the 
drill bit at the proper angle and cause the hole to develop along a new 
angle. The force angle and the new hole angle are not necessarily the 
same, as bit rotation creates an orthogonal reaction torque. 

When the time comes to deviate the hole, 
engineering data is required to orient the deflection tools accurately. 
First the directional engineer must know the present course of the hole. 
Since the directional surveys have been repeatedly taken and plotted, 
this information is available. Second, he must know where the next 30 
feet of the hole should bottom out. Third, he must know the degree to 
which the selected deflection tool is capable of deviating the hole. This 
can range from a fraction of a degree all the way up to 5° or more. 



6-83 



Common deflecting tools include whip- 
stocks, and down- hole motors on bent subs. Other less frequently- 
used tools are discussed in Section 6.4.3. 

Whipstocks are special wedges which, 
when properly oriented and anchored, force the drill bit to drill into the 
side wall near the bottom section of the hole. It is simply a long 
metallic wedge which is anchored or cemented into the bottom of the 
hole. A smaller diameter bit is used which follows the side of the 
wedge until it reaches the bottom. The whipstock then maintains the 
proper hole angle by warping the drill string. The small pilot hole is 
continued ten to thirty feet below the bottom of the old hole. Then the 
drill string and, usually, the whipstocks are withdrawn. A full gage 
reamer is placed behind the pilot bit, and the new hole is reamed to 
full size. The normal drillstring assembly is then attached and drilling 
continues at the new angle. This procedure is shown in Figure 6.40. 

Anchoring the whipstock can be a 
problem. Originally, whipstocks were cemented in and left in the hole. 
This technique has fallen in disfavor because of the possibility that the 
wedge will break loose in some future operation and jam in the hole. 
This can cause an expensive and time consuming fishing operation. 

Today's recoverable whipstocks operate 
with chisel point ends and fluid passages to wash any debris from the 
bottom before the whipstock is set. 

Initially, the tool is directly connected to 
the drillstring by shear pins. After it has been inserted in the hole, 
and oriented at the proper angle, sufficient force is applied to the drill- 
string to cause the pins to shear, and the chisel point to anchor the 
wedge. This procedure is not applicable to all formations. Frequently, 
in soft formations' the chisel will not provide a sufficiently firm anchor 
and the whipstock will turn with the drill. Resetting the whipstock now 
becomes an exercise in the ingenuity of the driller. The whipstock 



6-84 




Figure 6.40. Deviating a Hole with a Whipstock 



6-85 



frequently can be cemented with a plug in the bottom of the hole. How- 
ever, this will not always work; many factors are involved. There are 
some ground waters with mineral content that will not allow cement to 
harden properly. 

Temperature also plays an important 
role, for example, in current practice in drilling diver sional holes for 
mineral exploration cement hardens beautifully in Arizona, while in the 
Zinc- Tin Belt of Tennessee the cement never seems to harden. An 
ingenious technique frequently employed is to drive a dry, end grain, 
piece of wood into the hole, set the chisel point, then wait for the wood 
to swell, and lock the whipstock. 

The use of the down- hole hydraulic motor, 
on a bent sub has been increasing. The bent sub is simply a short 
section of drillstring with the threaded ends at an angle with each other. 
The drill string is attached to one end, the motor at the other. As 
with the whipstock, a number of surveys with angular corrections are 
required to orient the rotational angle of the bent sub. An additional 
factor in orientation rests in the fact that the down- hole motor generates 
a considerable reaction torque. This causes the drill string to twist to 
the left (counterclockwise) in opposition to the normal rotation of the 
motor. This angle must be taken into account in orienting the sub. 
The twist of the drill string is governed by the depth of the hole, the 
rigidity of the drill rod, and the torque of the motor. The torque in 
turn is governed by the fluid flow rate, the force on the bit, and the 
drilling characteristics of the formation. 

The ability to accurately deviate a hole 
with this technique depends upon close control of drilling parameters 
and frequent timely surveys. 



.-86 



6. 4. 3 Equipment 

The following sections describe directional 
drilling equipment. Survey devices, drill string stabilization equip- 
ment and deflection tools are discussed. Some additional information 
on the procedures employed with the various items of equipment are 
also included. 

6.4.3.1 Survey Devices 

(a) Magnetic Single Shot and Multi-Shot 

Devices 

The state-of-the-art in available 
survey instrumentation for horizontal drilling is typified by the magnetic 
multi-shot and single shot devices available from such companies as 
Eastman Whipstock Inc. and Sperry-Sun Inc. A typical magnetic multi- 
shot instrument is illustrated in Figure 6.41. These instruments have 
a 1.75 inch (44.5 mm) outside diameter. 

In addition to the survey device 
there is auxiliary- equipment which must be used in conducting a survey. 

In order to survey down hole, the 
instrument is normally mounted in a protective case with either spring- 
mounted or pneumatic shock absorbers. The case is selected for the 
size of the pipe so it can be pumped (go-deviled) down the drill string. 

Above the drill bit is a set of non- 
magnetic drill collars. Their length is selected so that the magnetic field 
will not be distorted by the iron of the pipe above, nor the drill motor 
or deflection tools below, the survey point. The common practice is to 
position the survey tool about one-third of the way up the collars. To 
accomplish this a series of non-magnetic extension bars are assembled 



6-87 



below the protective case. These come in assorted lengths, so that they 
can be assembled in combination to fit the particular lengths of drill 
collars being run. (See Figure 6.42.) 

In order to determine the orientation 
of the tool face with respect to the survey package, a male shoe alignment 
cam is attached by a sub to the steering tool. A mule shoe is a set of 
mating cams which are shouldered to guide the instrument into a certain 
angular orientation as it seats itself. The cam flanges of the reference 
portion of the cam mate with pins or shoulders on the tool to be oriented. 
Regardless of its initial orientation, they rotate it to the proper angle 
prior to seating. Some subs are available so that the mule shoe can be 
pin-aligned with the face of the steering tool. Others use scribe marks 
for the alignment. The angle between scribes must be measured. This 
then becomes a bias angle which must be subtracted out in subsequent 
computations. 

If the survey package is a single 
shot, it is retrieved by a wire line running through the swivel (rotating 
joint on the drill rig) which feeds the drilling fluid from the pump to 
the drill string. At the end of the wire line is an overshot. This is 
a self- engaging device which attaches itself to the head of the single 
shot. After the overshot is pumped down and attaches itself, the single 
shot is retrieved. If the device is a multi-shot, it is go-deviled down 
just before it is necessary to pull the drill string. Usually the timer 
is set to take a picture every 20 seconds as the drill string is removed. 
On development, those pictures which were taken while the pipe was 
moving will be blurred. It is necessary to stop the pipe each time a 
length of drill rod is removed. Thus, pictures taken during this interval 
will be clear. Some multi- shots also include a watch which is synchronized 
with a similar watch on the surface. Thus, correlation between the time 
shown on the pictures and the logged time for removal of individual 
sections provides an additional method of checking the location of multi- 
shot readings. 



6-89 



NON-MAGNETIC 
EXTENSION BARS 




NON-MAGNETIC 
DRILL COLLARS 



Figure 6.42. Typical Directional Instrument Assembly 

6-90 






(b) Gyroscopic Devices 

Humphrey Inc. builds both gyro- 
scopic and fluxgate magnetometer survey devices. This equipment can 
be ordered on a custom basis in configurations suitable for surveying 
horizontal holes. The equipment transmits data to the surface by wire- 
line and is monitored on a "real time" basis at the surface. A gyro- 
scopic survey system is illustrated in Figure 6.43. This equipment is 
typically 1. 75 inch (44. 5 mm) in diameter. 

(c) Survey Steering Tools 

Survey steering tools are survey 
devices which are pumped down the drill string to provide "real time" 
survey information when a direction change is carried out. The devices 
are basically magnetic survey instruments which transmit data to the 
surface through a wireline. A steering tool system is illustrated in 
Figure 6. 44. 

Survey steering tools are widely 
used for directional drilling operations in the petroleum industry where 
they have been instrumental in making the Dyna- Drill the preferred hole 
deflection tool. The continuous surface read out allows the driller to 
determine how much the drill string is twisting due to the reaction 
torque of the down-hole motor. This enables the driller to set the 
angle of the bent sub under dynamic conditions. He can then hold this 
angle by control of: the drill string orientation, the thrust of the bit, 
and the fluid flow rate. This is a truly dynamic reading, under full 
power. It takes the guesswork out of the survey setting. Thus, it 
provides a capability not achieved by any other means. 

One such system consists of a down- 
hole probe, surface data processor, digital mini- computer, tape printer, 
X-Y plotter, and angle read-out. Optionally, a digital cassette recorder 
is provided to record all data for future processing. 



6-91 







6-92 




Drill 
Rotating Bit Sub 



Figure 6-44. Survey Steering Tool 
6-93 



All equipment is field portable or is 
mounted in a truck which also contains a single conductor wire line unit. 

The probe utilizes magnetic sensors 
and accelerometers to determine the direction of the magnetic and gravi- 
tational vectors relative to the axes of the probe. A gyro can be used to 
replace the magnetic sensors if the survey is to be performed inside drill 
pipe or casing. The sensor data is conditioned and multiplexed by 
electronic circuitry contained within the probe and transmitted to the sur- 
face via a single conductor wire line. The wire line also provides power 
to the probe. 

At the surface, the sensor signals 
are reconstructed by a data processor. Tool or drill face alignment is 
provided directly to an angle readout for drill steering. Sensor data 
along with measured depth information is fed to a digital mini- computer 
where all necessary survey computations take place. Completed survey 
data from the computer is immediately presented by a tape print out and/or 
X-Y plot of the plan and elevation view of the hole. Simultaneously a 
recording of the survey data can be furnished for future computer 
processing. 

The computational speed and accuracy 
of the digital computer allows almost instantaneous print out of survey 
data to a high degree of resolution and repeatability which eliminates 
human errors in interpretation and computation. 

Survey steering tools are generally 
available for applications up to 70° from vertical. Horizontal versions 
of these devices are said to be available on a custom order basis, and 
several companies have indicated that they intend to provide them as a 
service in the near future. Scientific Drilling Controls, Inc. of Newport 
Beach, California and Sperry-Sun Inc. , of Houston, Texas manufacture 
survey steering tools and provide related services. These devices have 
a typical outside diameter of 1.75 inch (44.5 mm). 



6-94 



Survey device manufacturers are 
listed in Appendix A. 

6.4.3.2 Stabilization Equipment 

As noted in Section 6.4.2.2 stabilization 
equipment consists of (1) stabilizers, (2) drill collars, and (3) reamers. 
This equipment is supplied by manufacturers servicing the petroleum drilling 
industry. Drilco Division of Smith International, Inc., Midland, Texas is 
a major supplier of stabilization equipment. Listings of other suppliers 
can be found by consulting the references in Appendix A. 

6.4.3.3 Steering or Deflection Tools 

(a) The Whipstock 

The whipstock is a wedge-shaped 
steel casting with a tapered or concave guide channel for the bit (Figure 
6.45). Whipstocks can be permanently installed, or they can be of a 
removable type. The permanent whipstock is cemented in and remains 
in the hole. It was used in the early days of directional drilling, but is 
seldom used today. Experience has taught the drillers that circulation 
and drilling operations may loosen a permanently set whipstock and cause 
it to dislodge into the new hole. This could result in a costly fishing 
operation or even the loss of the hole. Except for very special cases, 
removable whipstocks are now used almost exclusively. 

The removable whipstock is an old 
reliable deflection tool, but it has some major disadvantages compared to 
down-hole motors. It does not allow a full gauge hole to be drilled. 
Its use requires considerable trip time because a small undersize rat- 
hole must first be drilled. The rat- hole must then be reamed to full 
size after the whipstock is removed. Although the whipstock is gradually 
being displaced by down hole motors, in certain cases it is still the best 
tool for the job. 



6-95 



COLLAR 



SHEAR PIN AND __ 
CIRCULATION BYPASS 



BIT 



STABILIZER 



NON-MAGNETIC 
LIMBER ASSEMBLY 



CHISEL POINT 



DRILLING, 

FLUID 




DRILLING FLUID 



Figure 6.45. 



Whipstocks: (a) Noncirculating Wh-^stock; 
(b) Cross Section of Circulating Whipstock 



(b) Knuckle Joints 

The knuckle joint (Figure 6.46 ) is 
basically a pilot reamer, (an undersize bit ahead of a full gauge bit) with 
a universal joint principle built into its connection with the drill stem. 
We have found no record of knuckle joints being used in existing hori- 
zontal holes. However, the reason for its lack of use seems to be that 
these tools are not made in the smaller gauges currently used for 
directional high-angle holes. The universal, which is usually a splined 
ball and socket joint, enables the lower drilling assembly, consisting of 
bit and reamer, commonly called the stinger, to rotate at a different 
angle from the drill stem. This changes the drift angle and direction 
of the hole. When the joint enters the new hole, the knuckle straightens 
out, and the drill pipe takes care of the necessary curvature for con- 
tinuing the hole in the new direction. 

As with other directional tools, 
the knuckle joint is oriented and set on the bottom in this position. The 
tool is worked in and out to form a recess for the lead bit on the stinger. 
When no more progress can be made, heavy thrust is applied, the tool 
is set and rotation is started at 20 to 40 rpm, with steady circulation. 
Drilling is continued until 15 to 20 feet of hole have been made. 

In operating the knuckle joint it is 
important to maintain proper force (weight) and to keep the tool cutting 
or biting into the formation. If this action slows up, the tool has a 
tendency to crawl around the hole and change its direction. Applying 
the weight is the only means of holding the desired direction. The 
knuckle joint gives greater deviations than the whipstock as the deflection 
takes place in a distance equal to the length of the tool. The deviation 
will vary with the formation and the manner in which the tool is being 
used. In slant drilling, the knuckle joint is commonly used in soft 
formations which will not hold whipstocks. 



6-97 



Figure 6.46. Knuckle Joint (Courtesy Houston 
Oil Field Material Co.) 



6-98 



(c) Spudding and Jet Bits 

These bits are used only in 
extremely soft formations. They are used to deviate holes where the 
formation can be directionally eroded by a jet of water. They do not 
seem to be used in high angle holes because of their relatively un- 
controllable washing action. This can cause the hole to collapse. 
Other bits and directional tools which lessen damage to the formations 
seem to be preferrable in high angle holes. 

(d) Down-Hole Hydraulic Motors 

Today the most common tools used 
to deviate a hole are the down-hole hydraulic motors, of which there are 
two types, positive displacement and turbine. Both, types of down-hole 
motors have several advantages over the older types of deflection tools. 

They drill full gauge holes so that no follow-up run to ream 
the rat- hole is required. 

Multiple deviations and corrections can be made without 
coming out of the hole. 

The motors can be made to clean out bridges in the hole, 
and can clean out bottom hole cuttings before deviation is 
started. 

They are unique in that they utilize the flow of drilling 

fluid down the drill string to turn the bit, thus eliminating the 

need to turn the drill stem. 

They drill to a smooth arc of curvature rather than 
a series of sharp, abrupt doglegs, associated with con- 
ventional wedging or whipstocking techniques. 



6-99 



The systems carry their own bending force along as they 
drill. Thus, they describe a smooth arc of a circle, the 
radius of which is established by the degree of fixed bend 
in the bent sub. 

(e) Down- Hole Turbine Motors 

Down-hole turbine motors (Fig- 
ure 6. 47)consist of a turbine section, a replaceable bearing section, and 
a rotating bit sub on which a conventional bit is made up. Turbines 
operate only with mud as a circulating medium. 

The turbine section contains blade- 
like rotors and stators. The stator is attached to the outer case of the 
tool and is held stationary by it. The rotor is attached to the drive 
shaft. Each rotor and stator combination are termed a "stage" and 
several stages constitute the turbine section. In operation, drilling 
mud is pumped down the drill string and into the tool. The blades in 
each of the stationary stators guide the mud onto the rotor blades at an 
angle. Mud flow forces the rotors (and thus the drive shaft) to rotate 
to the right. 

Turbine drills typically run from 
1,500 to 3,000 rpm. Thus, it is difficult to get a good match between 
their speed-torque characteristics and those of the bit. They are also 
very sensitive to loading of the bit, and will stall if overloaded. 

There are several directional 
drilling organizations using them. However, we have found no cases 
where they have been used for controlled directional drilling of hori- 
zontal holes. 

(f) Positive Displacement Motors 

Positive displacement motors 
differ from turbines in that they generate their motor action through 



6-100 



TUR8INE 
BLAD£S 



SEARING 
PACK 



DRIVE SHAFT- 



I TURBINE SECTION 



BEARING SECT/ON 



Figure 6. 47 - Downhole Turbine Motor 



6-101 



physical displacement rather than by the inertial impact of the fluid. 
They fall in the category of low speed hydraulic motors. Conceptually, 
there are many ways this action can be achieved. However, the only 
positive displacement down-hole motor in current use seems to be the 
Dyna-Drill. This is essentially a Moyno pump used in reverse appli- 
cation. The assembly is shown in Figure 6.21. It consists of a 
dump valve above the motor proper to enable the filling and draining of 
the drill string before and after operation, a three- stage motor assembly 
(comprised of a rotor and stator), a connecting rod assembly, a bearing 
and drive shaft assembly, and a rotating sub to which a conventional 
bit can be made up. 

The Dyna-Drill can be obtained 
either for use on a bent sub, or in a bent housing configuration. The 
design of the tool includes a flexible connecting rod, so that the drill 
housing can be bent at this point without affecting the tool's operating 
characteristics, Figure 6.48. With this modification the bend in the 

assembly is located much closer to the bit than with the conventional 
bent sub- assembly. 

There are several advantages to 
this configuration: 

There is less lateral displacement of the tool in the 
borehole. 

The tool is easier to orient. 

There is less damage to the borehole. 

The drill bit approach angle to the formation is 
increased. 

For any bend angle, the ratio of the angle changes 
to the length of hole drilled is increased. 



6-102 







Bent Housing Assembly 



Bent Sub Assembly 



Figure 6.48 - Bent Housing and Bent Sub Dyna -Drill Assemblies 
(Courtesy, Dyna -Drill Co.) 



6-103 



It provides a stiffer, more stable configuration. 

In operating both the turbine and the 
Dyna-Drill, there is a characteristic that other types of deflection tools 
do not have. This is the generation of reaction torque. Reaction torque 
is the result of the drilling fluid flowing against the stator, trying to 
rotate the drill string to the left while the rotor and bit rotate to the 
right. This phenomenon must be taken into account when orienting down 
hole motors. The direction in which the tool faces, as determined by 
a single shot survey will in general not be the direction it will go when 
drilling commences. 

Experience in a specific geological 
area, with a specific drill string, is the only way to truly learn how to 
compensate for reaction torque in that configuration. One rule of thumb 
often used is to allow 10 per 1,000 feet when drilling in soft formations 
and 5° per 1,000 feet for hard formations. In other words, the motor 
is faced 5° to 10° to the right (clockwise) for each 1,000 feet of hole 
length. Thus, when the motor is activated, reaction torque will turn 
the tool back in the proper direction. Even with the above rules of 
thumb, reaction torque presented a vexing problem until the advent of 
the survey steering tool discussed in Section 6.4.3.1. 

Manufacturers of deflection tools 
are listed in Appendix A. 

6.4.4 Guidance Capabilities 

For the most part, adequate statistical test 
data are lacking to evaluate what the limits of guidance accuracy are. 
No truly objective projection of what can be achieved can be made 
without such a base line. 



6-104 



Two reasonable samples of data have been 
obtained, one set for survey accuracy and one set for steering accuracy. 
Neither set is truly representative of the long-range horizontal drilling 
problem. However, they are adequate to establish a point of departure, 
to serve until better data are available. 

6.4.4.1 Survey Accuracy 

The state-of-the-art in horizontal 
and near horizontal survey instrumentation is represented by the single 
shot and multi-shot magnetic survey devices. 

In January of 1963, Sperry-Sun con- 
ducted a controlled experiment to determine the degree of accuracy of 
Sperry-Sun survey equipment. Hurricane Mesa, St. George County, 
Utah, near Zion National Park, was selected as the test site. A string 
of aluminum pipe was laid from the top along the mountainside of the 
Mesa. After an initial 250 foot (76 m) drop, the average angle of 
inclination was 55° over a course of 2580 feet (786 m) long. 

Tests were run on magnetic multi- 
shot and slim-hole gyroscope multi-shot devices. An independent survey 
organization was called in to survey the pipeline with third-order accu- 
racy. 

To fully exploit the checking and 
accuracy of Sperry-Sun directional survey services, a series of both 
continuous magnetic surveys as well as slim-hole gyroscopic surveys 
were run. 

In these tests different components 
of instruments were utilized to eliminate biases caused by individual 
units. Three (-3) different surveying engineers were used to eliminate 
interpretive biases that otherwise might cloud results. The gyro 
equipment is not available for horizontal surveying. A different gimbal 



6-105 



mounting would be required. Therefore, only the results of the mag- 
netic multi-shot will be discussed. 

Four surveys of the pipeline were 
made using the continuous magnetic multi-shot method. These consisted 
of three different runs at 30 foot (9 m) intervals and one run at 100 foot 
(30 m) intervals. The 30 foot (9 m) intervals could be expected to give 
better statistical accuracy, but the 100 foot (30 m) interval was run as 
more representative of oil field operations. 

Figure 6.49 is a picture of a 0-90° 
display of a magnetic multi-shot. It can be read to an accuracy of 
about + 1/2 degree in elevation and probably a little better than one 
degree in azimuth. An estimate of a combined reading error of one 
degree would seem reasonable. 

With a survey interval of 30 feet 
(9 m) a 2580 foot (786 m) run would have 86 points, while a 100 foot 
(30 m) interval would provide 25 points. 



The equation for total error, e, in 



feet is: 



e 



+ <t&» h< N > 1/2 + v N >] 



Whe 



re 



£ = Root Mean Square (rms) Error in Feet. 

e f = Fixed Offset Error in Feet (normally negligible) 

e = Resulting Error in Degrees (random errors) 

e , = Bias Error in Degrees (mostly calibration error) 

I = The Reading Interval in Feet 

N = The Number of Stations Read. 



6-106 




Interpretation: 

Inclination = 37 ° 
Direction = 0° Magnetic 



Figure 6.49. 0-90° Compass Angle Picture 



6-107 



Since these tests were initiated to 
establish a baseline instrumental survey, it is safe to assume that all 
possible steps were taken to eliminate both calibration and bias errors. 

Thus, we can assume the following: 

£ £ = % " ° 

I = 30 ft. (9 m), N = 86, and 
I = 100 ft. (30 m), N = 25. 

For these conditions: 

e = .0175 I e r (N) 1/2 ft. 

or 

e m 4.85 feet for the 30 foot (9 m) interval 
and 

e = 8.73 feet for the 100 foot (30 m) interval. 

Figure 6.50 is a planview of the last fifty feet of the survey. The 
rms error of the three, 30 foot (9 m) interval runs is 5 feet (1.5 m). 

It is dangerous to try to extrapolate 
data from a 50° inclination to the horizontal or 90° inclination, because a 
completely different set of parameters becomes dominant. The basic high- 
angle compass, (0-130°) card (Figure 6.51) has somewhat better resolu- 
tion than the 0-90° card. Possibly a basic resolution of + . 25 degrees 
with an operational reading accuracy could be achieved. Bias errors 
will probably predominate if a reasonable survey increment is used. 
In general, maximum bias errors would be expected to fall within + 1° 
in elevation and + 2.5 degrees in azimuth. These would be under 
normal operating conditions, where results can be expected to degrade. 



6-108 



South 

of 
Start 



1890 



1900 - 



1910 - 



1920 _ 



1930 




930 



920 



— I r- 

910 
West 
of — 
Start 



900 



~I — 
890 



880 



Figure 6.50. Sperry-Sun Calibration Accuracy Determination 



6-109 




Interpretation: 

Inclination = 109 3/4° 

Direction = 9° Southwest 
Magnetic 



Figure 6.51. 0-130° (High Angle) Compass Angle Picture 



6-110 



For utmost accuracies, field procedures can evolve which would probably 
diminish these bias errors by a factor of four or five to minimum 
values in the order of 4-. 25° in elevation and possibly +.5° in azimuth. 
These procedures will require repeated calibration, and exploitation of 
any peculiarities of the local conditions. 

Claims for gyroscopic survey accu- 
racy equipment are about an order of magnitude better than magnetic 

instruments. |+ 1 ft (0.305 m) deviation for 1,000 ft (305 m) linear 

1 29 l~~ 
distance. However, this equipment must be custom built for hori- 

zontal applications and its probable cost is 2 to 4 times that of avail - 

33 
able magnetic survey devices. " In addition, the devices have not yet 

been proven in horizontal applications. 

The survey steering tool would be 
a valuable aid in controlling the accuracy of direction changes. How- 
ever, as in the case of gyroscopic survey instruments, the device must 
be custom made for horizontal applications and it has not yet been 
applied to the horizontal drilling problem. Daily charges for total 

costs associated with survey steering tools can run to 20 times the 

32 
cost of available magnetic survey tools. 

6.4.4.2 Steering Capability and Accuracy 

Review of horizontal drilling case histories 
leads to the conclusion that there are essentially three available state-of- 
the-art techniques for steering horizontal drilling. These include: 

(1) Variations in drilling assembly configuration along with 

adjustments in rotational speed and thrust to achieve 
vertical deviation control. (The fulcrum principal.) 



6-111 



(2) Use of the whipstock or wedge to control vertical and 
azimuthal deviation. 

(3) Use of the Dyna-Drill with a bent sub or bent housing 
to control vertical and azimuthal deviation. 

The fulcrum principal has proven success- 
ful in horizontal drilling programs conducted in soft materials with both 
diamond coring bits and rolling cutter bits. (Items 4, 15, and 17, 
Table 2.1) The effectiveness of this procedure has not been determined 
in medium and hard rock. 

Whipstocking (wedging) has been employed 
in all long horizontal drilling in medium and hard rock conducted with 

diamond coring equipment. (Items 2, 3, 5, and 16, Table 2.1) Whip- 

1 1 29 
stocking has been noted to be relatively ineffective in soft materials. ' 

The 1.7 5 in. (44.5 mm) Dyna-Drill has 
been an effective deflection tool in soft materials with both diamond and 
rolling cutter bits but information on its performance in medium and 
hard rock is lacking. The 5 in. (127 mm) Dyna-Drill has been effective 
in deflecting horizontal holes drilled in soft materials and angle holes 
in soft, medium, and hard rock. 

Table 6.8 is a summary of the drilling 
accuracies of twenty holes made by the Atomic Energy Commission. All 
these holes are in' the same locality. Thus, conditions are probably as 
thoroughly standardized as possible to provide a reasonable base line 
estimate. 

If these data are classed into two groups 
by date, the holes drilled between 1967 and the end of 1971 have a mean 
error of 26.8 feet.. The holes drilled in 1972 and 1973 have a mean 
error of only 6.2 feet. There seems to be a very obvious learning 
curve effect. 



6-112 



T-. 
c 

—I 
Cu 
X 

t-» r-1 
+-» V) 

o es 

•H 4-> 

U <D 
O bO 

sc *-< 

•Oh 
C 

o c 
J-l « 

»* trt 
O <D 

C O 

bOi-t 

C rH 
O.H 
»-J U 



Q 

W 

H 

W W 

< d< 

o 
o 



HJ 


W < 


rj U 


CXIt-H 


<H 


H c* 


w 


► > 



o 

§£ 

E-O 

«< rN» 
i— i t— i 

w o 



a: 


E-> 


P4 E- 


W W 


n w 


ti, 


w 


hJPs: 


o»-t 


X 



NOOaOlCnOX^OHHHNN I N N (N M N tO 



HNHMONOOHHNrftONCOCOH 



■a u 

O i-i 



re a: 

0>-hOOOOOv-< 

h5I JhJJJJI 



& U ~= 
OhO 



HCOdOtNO^COWHOOfOOlNtT, 



^■OOWOvSNH 



HHE-HHHhHt-t-HHE- 



■K 
* 

E- H E- 



« ► LT5- - HvOvOMO> tOvO I CT> G1 vC 



H tO 



OHNMO^OOONW^OO^OUI'd-OCC^IO 
(00^<*OOU)WCOHCOOOIONffl^NTW 

r^i-H<Njrv3 ,_< ^ ,_( ,_! ,_( (vj h to m -^ -> n 



HHHNrOHNHNMHHNNNH 



T-IOOOOr- Ir-IOOOOf— It— I r— I r-l O O — - 



Z>Z1Z}Z3Z>Z>ZD^Z3^^>ZDZ>^^^~~-^ 



6-113 



Figure 6.52 is a plot of this data. There 
seems to be no observable angular error as a function of distance. It 
is believed that these holes have probably not penetrated to a depth where 
the angular effect has become appreciable. As holes get deeper and 
torsional and frictional affects become greater, the errors can be expected 
to increase. This data could only be considered typical of small diameter 
diamond core drilling with whipstock steering. 

The early data from these holes is probably 
more representative of what could be obtained in a new hole in an undefined 
location. Thus, on the average, this hole could be expected to be steered 
within a 3 0-foot (9 m) radius. It would seem reasonable that the later 
data could be considered representative of an experienced crew, working 
to achieve the utmost in accuracy. Thus, steering to within a 6-foot 
(1.8 m) radius should be a realistic goal. However, re-direction and 
re-drilling portions of the hole would have to be expected. 

6.4.4.3 Conclusions 



When survey and steering error are 
combined, total guidance error in feet is: 



V E s + <T& 



V E s ' nfo> 2 < E C L " + E R LI > 



where 



E Total error in feet. 

Eq Steering error in feet. 

e Calibration error in degrees. 

e Random error in degrees. 

L Hole length in feet. 

I Survey interval in feet. 



6-114 



100 



o 
u 

w 50 "| • ^Mean of Early 






Holes 26.8 ft, 



u m w ^Mean of Later 

S o • # ° n V H ^ les 6 - 2 ft 



1000 




2000 


3000 


Hole Length ■ 


■ Ft. 




•Holes Prior to 1972 
oHoles 1972, 1973 



Figure 6.52. Steering Error Versus Length 



6-115 



4) 


on 


i—4 


J-i 


at 


4) 


> 


1) 


'd 


a 


4) 


at 




Jn 


O 


at 


0) 

g- 

u 


bo 






rj 


Fh 


M 


0) 


13 


4> 






Q 


CO 


a 


Ti 


% 


at 


■a 


rj 


nt 






>* 


§ 


4> 

> 

Fh 


a 


3 


w 


at 


h 


2 





o> 




vO 




a) 








rO 




at 




H 





Nominal Value 

Feet/Degrees 

(Meters) 




•i-i 

s 

0) 

w 


± 6 (1.82) 


o 


a 

•H 

< 


CX> 

,_J 1 1 

+1 


Minimum Value 

Feet/Degrees 

(Meters) 




! 

W 




1 
s 


cm 
+1 +1 


Maximum Value 

Feet/Degrees 

(Meters) 


o 
> 
W 


+1 +1 


a 

< 


i tn 

+1 +1 


at 

•H 

u 





6-116 



(saarpui) 







i— 1 i—4 


O 




| 


1 1 I 




o 
o 


4-> 

_o * 

CO 



"5 H 

Q 

in rt 

O 0) 

"12 > 






o 
m 








— '" ^ 




o 

IT) 

o 
o 




o 
o 

04 


"vO 






o 

IT) 

o 
o 


CO +j 






o 


ZL § 

•rt 
> 

o 3 

- en fl 

— - o 

— "* o 


~ 1 ^^ XS a-^Smny r ~ 




o 

LO 

o 
o 

o 
in 






o 
o 

(M 


" vO 


1 1 1 1 





U 

u 
ni 

<3 



w 



;j; ^8u8T axon 
6-117 



Table 6.9 indicates maximum and 
minimum or nominal values for the appropriate parameters projected 
from Sections 6.4.4.1 and 6.4.4.2. When these numbers are plugged 
into the equation above, the results can be plotted as maximum and 
minimum anticipated guidance errors as in Figure 6.53. 

6. 5 Fishing 

The term "fish" is used to describe any piece of equipment 
in the bore hole which the driller does not want in the hole and which 
cannot be retrieved at will. The term "fishing tool" applies to special 
equipment which is added to the drill string to engage and retrieve the 
fish. The term "fishing" applies to the application of fishing tools and 
associated procedures to remove the fish from the bore hole. The dis- 
cussion which follows owes- much to the Rotary Drilling Handbook by 

34 
J. E. Brantly. Chapter XXI of this reference presents a detailed 

discussion of fishing procedures. 

6. 5. 1 Causes of Fishing Operations 

The most common cause of fishing jobs is a drill 
string failure which results in the string breaking in two. This is 
commonly referred to as a "twistoff ". The section of drill string above 
the break can be withdrawn in the usual manner, but a fishing operation 
is required to recover the section of drill string below the twistoff. 

Another common cause of fishing jobs is sticking 
the string. If excessive torque or tension are applied to free the drill 
string a break can occur. Normally, if the string cannot be freed, it 
is intentionally separated by reversing the drill string rotation. A 
fishing operation is again required to remove the drilling equipment below 
the point of failure or intentional separation. 

Bit failures are another common cause of fishing 



6-11! 



jobs. Bit components from failed bits are practically undrillable and 
must be removed before drilling can resume. 

Other causes of fishing jobs are the loss of 
instruments in the hole and wireline breakage. 

6.5.2 Prevention of Fishing Operations 

The incidence of twistoff failures can be decreased 
by careful torquing of drill pipe connections and frequent inspection of 
drill string components. 

The most important element in preventing stick- 
ing of the drill string is careful control of the drilling mud program. 
The ability of the drilling mud to stabilize the hole and its lubricating 
properties are factors in preventing sticking of the string. 

Bit failures can be avoided by ensuring that 
the proper bit weight and rotational speed are employed. Bit perform- 
ance must be carefully monitored so that worn bits are replaced before 
they fail. 

6.5.3 Fishing Tools 

Primary fishing tools include: 

(1) Rotary taper taps and rotary die collars. 

(2) Circulating and releasing overshots. 

(3) Fishing magnets. 

(4) Junk baskets. 

Rotary taper taps (Figure 6.54(a)) have tapered 
case-hardened male threads which screw into a fish, and rotary die 
collars (Figure 6.54(b)) have tapered case-hardened threads which screw 
onto a fish. Both devices are used to retrieve lost sections of drill string. 



6-119 



(a) Rotary Taper Tap (b) Rotary Die Collars 



Figure 6. 54 - Pri mary Fishing Tools ( C ourtesy, Houston Engineers , Inc. ) 



6-120 



The single bowl and double bowl releasing and 
circulating overshots (Figure 6. 54 (c)) are lowered over the fish to 
grasp it. The overshot can engage and release the fish as often as 
may be necessary to free it, giving it a clear advantage over the non- 
releasing taper taps and die collars. The circulating overshot is sealed 
to the fish when engaged so that circulation may be resumed to aid in 
freeing the fish. 

Fishing magnets are used to retrieve broken bits 
and other smaller objects from the hole (Figure 6. 54(d)). 

The junk basket (Figure 6. 54 (e)) is made up of 
a long hollow barrel and a shoe on the lower end with hard-faced teeth 
capable of drilling into hard formations. Inside the shoe is a catcher 
having hinged fingers. The junk basket is lowered over the fish and 
rotated so that the shoe cuts a core from the formation. The hinged 
fingers of the catcher fold back as the tool is being rotated and driven 
over the fish and the core. When the junk basket is pulled back, the 
fingers of the catcher dig into the core and cut off a section, thus 
retaining the fish and core within the barrel. 

The tools described above are designed to engage 
the fish and permit force to be exerted on it so that it may be with- 
drawn from the bore hole. 

There are a number of other important fishing 
tools, sometimes called accessory fishing tools, which are used to aid 
and safeguard the operation of the basic engaging tools, to provide 
means for exerting unusual forces against the fish, to loosen the fish 
or separate it into removable lengths, or to prevent the need for fishing 
jobs in the first place. Fishing tools which fall into this category 
include rotary jars, bumper subs, safety joints, free point indicators 
and backoff shots, wash-pipe, external cutters, bumper safety joints, 
and jar safety joints. These tools are discussed below. 



6-121 




KEY 





(c) Releasing and Circulating Overshots 



Figure 6. 54 - Primary Fishing Tools - Cont. (Courtesy, Hendershot Tool Co.) ; 



6-122 




Optional Guides 



Lipped Guide 



t s w 



Mill Guide 
(d) Fishing Magnet 




(e) Junk Basket 



Figure 6. 54 - Primary Fishing Tools - Cont. (Courtesy, Bowen Tools, Inc. ) 



123 



(1) " Rotary Jars : Rotary jars are installed 

in fishing strings to enable the driller to strike heavy upward blows 
against an engaged fish to jar it loose from its stuck position. They 
are also included or made up in strings during testing, coring, and 
washing- over operations to act as safeguards and to provide the means 
with which to loosen the string should it become stuck. 

"All rotary jars have in them a restrain- 
ing mechanism which holds the telescopic elements of the tool in a 
closed position until sufficient upward pull is exerted to trip the restrain- 
ing mechanism and allow the telescopic elements to move into their 
extended position. In operation, the strain of the upward pull will 
stretch the drill pipe and, when the jar trips, the upward surge of the 
drill pipe in returning to its normal length will cause it to strike a 
severe blow. In order to concentrate the jarring blow at the fish and 
make it effective, it is important to include several drill collars in 
the fishing string immediately above the jar. 

"Some rotary jars depend upon the con- 
stant maintenance of torque in the string to trip their restraining mech- 
anisms. Other more widely used rotary jars incorporate simple mech- 
anical or hydraulic restraining mechanisms, and are tripped with a 
straight upward pull of the fishing. (Figure 6.55(a).) 

(Z) "Bumper Subs : To assure the driller 

further of the ability to release the overshot in the event it proves 
impossible to pull the fish, it is good practice to install a bumper sub 
in the fishing string immediately above the safety joint. Most bumper 
subs are merely expansion joints whose two sections are free to move 
vertically in relation to each other, but are prevented from rotating 
independently. With this tool in the string, the driller or the man on 
the brake is able to deliver the sharp downward blow which is required 
to break the engagement of the gripping member of the overshot with 
the fish, and the bumper sub will also transmit the torque required to 
complete the releasing operation. The presence of a bumper sub in 
the string is also definitely advantageous in releasing the overshot from 
a recovered fish at the top of the hole. It simplifies the operation and 
eliminates the necessity of resorting to awkward and dangerous measures 
(Figure 6. 55(b). ) 

6-124 



£ /wye 



Nwarausoc 

F1U.WJG 



< 



/.CONE 
jl.StLl 



no* dohum 



-BOTTOM SUB 



) Rotary Jar (Courtesy, Bowen 
Tools Inc. ) 



(b) Bumper Subs (Courtesy, Baash-Ross 
Div. , Joy Mfg. Co. ) 



(c) Safety Joints 



Figure 6. 55 - Accessory Fishing Tools 



6-125 



(3) "Safety Joints: The sole purpose of the 

many types of safety joints is to provide the fishing string operator 
with a connection readily releasable at any point in the string at which 
it is placed. Such tools provide definite safety advantages in both fish- 
ing and drilling operations. 

"The importance of using a 'releasing' 
overshot to retrieve a lost section of the drilling string has been 
stressed previously herein. As a precautionary measure against the 
possibility of failure on the part of the overshot' s releasing mechanism, 
it is good practice to install a safety joint in the fishing string and to 
locate it immediately above the overshot. Neither tool is adversely 
affected by the other, because overshots are released with rotation in 
a screwing (right-hand) direction and the safety joints are released 
with rotation in an unscrewing (left-hand) direction. Thus the driller 
has double assurance of the ability to disconnect and withdraw his 
entire string should it be found impossible to pull the fish. 

"Safety joints, the outside diameters of 
which correspond to the outside diameters of the tool joints in the drill 
pipe, should be selected. This will simplify any fishing operations 
which might necessitate engagement of the safety joint with an overshot. 
In order not to impair circulation and to permit the running of wire 
line equipment, the inside diameter of the safety joint should be equal 
to the inside diameter of the tool joints on the drill pipe. 

"In washing-over operations, it is good 
practice to install a special safety joint, called a washover safety joint, 
at the top of the wash-pipe. If the wash-pipe should stick, this tool 
can be separated and the portion of this special safety joint which is 
left in the hole has the same inside diameter as the wash-pipe. Thus 
there will be no impairment at the top of the fish, and proper tools 
can be lowered into the stuck wash-pipe to perform recovery operations. 
(Figure 6.55(c).) 



6-126 




Type B Super 



TypeM 



(c) Safety Joints 



Figure 6. 55 - Accessory Fishing Tools - Cont. (Court e sy, Homco 
International, Inc. ) 



6-127 



(4) "Freepoint Indicators and Backoff Shots ; 
As the name implies, freepoint indicators are lowered into stuck strings 
and operated to determine the lowest point at which the string is free. 
Thereafter, the weight of the unstuck portion of the string is picked up 
the left-hand torque is applied, and a companion tool, called a 'backoff 
shot, ' is detonated within the lowest connection of the free portion of 
the string. The combination of these forces will cause the tool joint to 
back off and separate the drilling string at this point. 

"All freepoint indicators have contact 
points at the upper and lower extremities of the tool, and these contact 
points engage the inside of the drill pipe either mechanically or magnetic- 
ally. The tools are electrically operated and, when their contact points 
are in engagement, an upward pull in the string will record a degree of 
stretch if the string is free and no stretch if the string is stuck. Thus, 
by setting the instrument at various depths in the drilling string, and 
then stretching the string, it is possible accurately to locate the lowest 
point at which it is free. 

"Whenever it becomes necessary to 
separate a stuck string, it is important to do so at the lowest point in 
order to leave as little as possible for subsequent recovery. (Figure 
6.55(d). ) 

(5) "Wash-Pipe: Wash-pipe and rotary shoes 
are used to cut clearance between a stuck fish and the walls of the hole 
to loosen it and to permit its removal. 

"The pipe selected to perform this opera- 
tion must have an outside diameter small enough to operate in the drilled 
hole, and an inside diameter large enough to pass over the fish. Though 
threaded and coupled casing is frequently used for wash-pipe, the torque 
strains of the operation often exceed the limits of these connections. 
Special washover pipe or wash-pipe casing with shouldered connections 
is recommended. 



6-128 



DESCRIPTION OF THE 

DIA-LOG "FPI" FREE 

POINT INDICATOR 

A. WEIGHTS: Ample weights are r 
above the tool to 
of the belly springs and assure passage 
of the tool through heavy 




C. UPPER & LOWER BELLY SPRING 
ASSEMBLIES: The Electronic Indicating 
held in place in the pipe by 
two sets of adjustable belly springs. Use 
of coil springs in combination with the 
flat belly springs assures greater spring 
flexibility, permitting the tool to pass 
through comparatively small openings 
without losing its holding power in 
larger pipe. For example, with the 
springs set to hold in 4Vi" drill pipe, 
the tool will operate efficiently in 2" 
I.D. drill collars— or will pass through 
openings in fishing tools as small as 
1%" I.D. Weight of the tool itself (less 
weights and jars) is only 16 lbs. -a 
weight easily supported by either set of 
belly springs. 

D. ELECTRONIC STRAIN GAUGE ELE- 
MENT: This highly-sensitive strain gauge 
measures stretch and torque movement 
in the pipe, and transmits the signal to 
the surface equipment. 



DIA-LOG COMBINATION FREE POINT 
INDICATOR AND BACK-OFF SERVICE 

The Dia-Log String Shot Back-Off can be 
run in combination with the Dia-Log Free 
Point Indicator (as shown at left) to recover 
any size of stuck drill pipe, drill collars, wash 
pipe or tubing. By applying reverse torque at 
the connection to be backed-off — and firing the 
Dia-Log String Shot across this connection— 
the desired joint can be unscrewed. The Back- 
Off shot is positioned at exactly the right place 
across a connection by means of the electronic 
Dia-Log Collar Locator. 

A Back-Off can be accomplished in straight 
or directional holes, and in holes where high 
temperatures and high pressures are encoun- 
tered. The explosive jar is specially designed 
to prevent any damage to the pipe or to the 
threaded connection. 

A Dia-Log String Shot may be run in com- 
bination with any of the three sizes of Dia-Log 
Free Point Indicators described on the facing 
page. By using the Combination Free Point In- 
dicator and Back-Off Service one run is all that 
is required to determine the deepest point of 
free pipe and to effect recovery of the pipe at 
the deepest free connection. 



Illustrated at left is a typical Dia-Log Combination 
Free Point Indicator and String Shot Back-Off assembly 
lor both indicating the deepest tree point of the stuck 
pipe and pin-pointing the desired connection to be 
backed oft — both on one trip into the hole, thus saving 
valuable rig time and increasing operating efficiencies. 
"A" is the electronic Collar Locator, "B" is the Dia-Log 
Free Point Indicator (described in greater detail on 
page 1361) and "C" is the String Shot that effects 
recovery of the stuck pipe (in conjunction with reverse 
torque) at the deepest free connection. 



(d) 

Figure 6. 55 - Accessory Fishing Tools - Cont. (Courtesy, The Dial-Log Co. ) 



6-129 



"The hole conditions and the amounts of 
clearance which exist between the wash-pipe and the drilled hole and 
between the wash-pipe and the fish are important factors in determining 
the length of fish which can be washed over safely in any one run. 
Crooked holes and tight clearances restrict safe operations to short 
strings of wash-pipe. Straight holes and generous clearances permit 
the safe operation of longer strings of wash-pipe. 

"The rotary shoe which is installed at 
the bottom of the wash-pipe should have hard-faced teeth of the proper 
type to cut the material against which it will be lowered and rotated. 
The tooth form should be coarse if the formation is soft, and fine if 
the formation is hard. If metal is to be cut, the teeth should be faced 
with granular tungsten carbide. The outside diameter of the shoe should 
be larger than the outside diameter of the wash-pipe, and the inside 
diameter of the shoe should be slightly smaller than the inside diameter 
of the wash-pipe to protect the latter from sticking. (Figure 6.55(e).) 

(6) "External Cutters: External cutters are 

resorted to when all other means have failed, and a stuck string of drill 
pipe can be recovered only by cutting it into removable lengths. 

"The fish must first be washed over in 
the usual manner. Then an external cutter is installed in the bottom of 
the wash-pipe in place of the rotary shoe and run into the hole and 
lowered over the stuck drill pipe to the proper depth. A cutting opera- 
tion is then performed and, upon its completion, the cut section of the 
drill pipe will be retained inside the wash-pipe by the external cutter, 
and it will be recovered as the wash-pipe and external cutter are pulled 
from the hole. These steps must be repeated until all of the stuck 
drill pipe is recovered. (Figure 6.55(f).) 



6-130 












o 




o 



o 
o 



(e) Rotary Washover Shoes 



Figure 6.55 - Accessory Fishing Tools - Cont. (Courtesy, Tri -State Oil 
Tool Industries, Inc. 



6-13 1 



FIG. 178 
External Upset Joints. 
Dogs catch under the 
upset, actuating the 
knives and also retain 
the cut-off pipe. 



FIG. 177 
API JOINTS. Overshot 
Spring catch under a 
tool joint or coupling 
to actuate the knives 
and retain the cut-off 

section. 



FIG 179 
External Flush Joints 
Straight Slips grip into 
flush pipe at any point, 
both actuating the 
knives and retaining 
the cut-off pipe. 



(f) External Pipe Cutter 



(f) Internal Pipe Cutter 

Figure 6. 55 - Accessory Fishing Tools (Courtesy, Baash-Ross Div. , 

Joy Mfg. Co. ) 



6-132 



(7) "Bumper Safety Joints: Bumper safety joints 
are combination tools which provide the services of both a bumper sub 

and a safety joint. Thus, at the will of the operator, they can be 
operated to deliver heavy downward blows, or they can .be separated. 

"They are used most effectively in 
drilling strings to prevent fishing jobs or to simplify them if they do 
occur. With a bumper safety joint in place, if the drilling string is 
pulled into a keyseat as it is being withdrawn from the hole, or if it 
should stick from any other cause, it is probable that this tool can 
loosen the stuck pipe. Otherwise, the tool can be separated and the 
fishing job is probably simplified. 

(8) "Jar Safety Joints: Jar safety joints are 
combination tools which provide the services of both a rotary jar and a 
safety joint. In other words, they can be called upon to deliver heavy 
upward blows or they can be separated at the will of the operator. 

"Because of these dual characteristics, 
these tools are widely used as safety devices to prevent fishing jobs 
completely or to simplify them when they do occur. With a jar safety 
joint in place during drilling, coring, testing, or washing-over opera- 
tions, it is most probable the string can be jarred loose should it 
stick -- and, if not, the tool can be separated and the fishing job thereby 
simplified." 

6.5.4 Conclusions 



The tools and procedures described in Section 
6.5.3 have been developed primarily for petroleum drilling; in other 
words, vertical and near vertical drilling. This equipment and the 
procedures associated with its use should be applicable to horizontal 
drilling as well. However, fishing experience is very limited in hori- 
zontal drilling and documentation in this area is practically nil. Jacobs 
Associates did report several instances of successful fishing jobs on 
their horizontal drilling program. These jobs involved the retrieval 

of twistoffs, and a rotary taper tap was the fishing tool used. At this 
point we must assume that fishing operations in horizontal drilling will 

6-133 



follow petroleum drilling practice. Fishing tool suppliers and fishing 
service companies are listed in Appendix A. Further detail on fishing 
practices in petroleum drilling can be found in Chapter XXI of Brantley. 

6. 6 Sample Taking and Retraction Techniques 

One of the most likely purposes of a horizontal drilling 
project is to obtain core samples along the proposed tunnel alignment. A 
second requirement prescribed for this study is to investigate techniques 
for recovering undisturbed samples from gouge. The state-of-the-art 
of techniques to accomplish these tasks in horizontal bore holes is 
discussed in the following sections. 

6.6.1 Core Sampling 

The "standard" technique for obtaining core samples 
in long horizontal drilling is the diamond wireline technique. The standard 
wireline core barrel has a bearing system which allows the inner tube, 
which accepts the core, to remain stationary while the outer tube rotates. 
This allows good recovery in a wide range of formations. Triple tube 
wire line core barrels have a third chrome plated, low friction tube 
located inside the inner tube. This allows good recovery in highly crushed 
or fractured formations. 

Exploration type wireline core barrels are available 
in the A thru P sizes. Table 6.10 gives the hole diameters and core 
diameters corresponding to these letter notations. As noted in Section 
6.1.1, the B and N size barrels are the most widely used sizes for horizontal 
drilling. Suppliers of wireline coring equipment for the exploratory field 
are listed in Appendix A. 

Diamond wireline equipment has been developed for 
core sampling in the petroleum field. The equipment consists principally 
of coring bits and core barrels which are substituted for the rolling cutter 
bit on a rotary drilling system. Coring bits for this application are avail- 
able in outside diameters from 4 to 12.25 inches (102 - 311 mm). Cores 

6-134 













TABLE 


6. 


10 








WIRELINE CORE 


BARREL 


SIZES 






AQ 


BQ 




NQ 


HQ 


PQ 


Size of Barrel 


Inches 


Inches 




Inches 


Inches 


Inches 




(mm) 


(mm) 




(mm) 


(mm) 


(mm) 


Hole Diameter 


1 Z4 


2 23 
2 Z4 




2 63 
2 ^4 


i 

! 3 " 
! 32 


4 53 
4 T^4 




(48) 


(60) 


j 


(75.8) 


! (96) 


(122.6) 


Core Diameter 


^ 


i£ 




'* 


»4 

i 


3ii 

* 32 




(27) 


(36.5) 




(47.6) 


(63.5) 


(8 5) 



6-13 5 



from 1.75 to 5.25 inches (45 - 133 mm) in diameter and lengths to 60 feet 
(18 m) may be obtained with this equipment. Sleeve type core barrels 
which protect the core from washing are available to improve recovery 
in soft or broken formations. To our knowledge this equipment has not 
been applied to horizontal drilling. 

Milled tooth and insert type rolling cutter bits have 
been used as coring bits in vertical drilling. Scripps Institute of Ocean- 
ography has reported good results in wireline core drilling with insert 

35 
type rolling cutter bits. 

The continuous core drilling technique discussed in 
Section 6.1.5 has also been a successful technique for obtaining core 
samples in vertical applications. With further development work, this 
technique should be a viable technique for obtaining continuous core 
samples in horizontal drilling. 

6.6.1.1 Split Tube Core Barrels 

Split tube core barrels alleviate the 
problems encountered in trying to remove fractured or fragile core 
samples from a solid core barrel. Figure 6.56 illustrates a split tube 
core barrel and incidates how the split tube barrel separates to allow 
core evaluation. Among the claims made for the split tube core barrel 
are: 

(1) The undisturbed or as-drilled 
quality of the recovered core 
permits a near in situ evalua- 
tion of the core. 

(2) The core is easily transferred 
from the inner tube to the core 
box without disturbing the 
sample. 



6-136 






(3) The split tube design facilitates 

the removal of expansive or 
sticky formations from the inner 
tube. 

Split tube conversion kits are available 
for both wireline and conventional core barrels. Conversion assemblies 
are available for the B, N, and 3.5 x 2.125 inch (89 x 54 mm) sizes. 
Lengths of 5 (1.5 m) and 10 feet (3.1 m) are available, except for the 
B size, which is available in 5 ft (1.5 m) lengths only. Kit costs can 
run from about $220 per core barrel for the smallest sizes to $340 for 
the largest. 

Christensen Diamond Products of Salt Lake 
City, Utah offers split tube core barrel conversion kits. 

6.6.1.2 Techniques are available to determine 
the in situ orientation of a core sample. Core orientation services 
utilize nonmagnetic core barrels with special tungsten carbide inserts. 
(See Figure 6.57(a).) The carbide inserts scribe a reference mark on 
the core sample as the core is drilled. (Figure 6.57(b).) A magnetic 
survey instrument is attached to the core barrel to record hole inclina- 
tion, bearing, and the orientation of the scribed reference mark. 

After the core is recovered, a core 
Goniometer (Figure 6.58(a)) is used to physically orient the core relative 
to its original position in the formation. The core can then be analyzed 
to determine the dip and strike of the bedding, foliation, cleavage, 
healed or broken joints, contacts, and shears. Thin sections for use in 
further studies may also be taken. (Figure 6.58(b).) 

Another method of reading the oriented 
core is to assume a plane through the scribe line and the axis of the 
core and measure all geologic features in reference to this plane and 



6-137 



and the length of the hole. Each point of measurement, or the attitude 
of a plane measured in reference to the axis of the core, can be rotated 
to its correct position in space and the position determined by use of a 
Schmidt Equal Area net. This procedure has been computerized and is 
offered as a service by Charles S. Robinson and Associates of Denver, 
Colorado. 

Core orientation is available as a service 
for B, N, 4. 5 x 3 inch (114 x 76 mm), 5. 75 x 4 inch (146 x 102 mm), 
and 7. 5 x 5. 875 inch (191 x 149 mm) size core barrels. Charges are 
about $3 25 per day for the B and N sizes and $260 per day for the 
larger sizes. Standby charges for the service are about $87 per day. 
Tools can be rented for about $150 per day. 

Core orientation service is available 
from Christensen Diamond Products of Salt Lake City, Utah and Charles S. 
Robinson and Associates. 

6. 6. 2 Undisturbed Gouge Samples 

Two techniques for obtaining relatively undisturbed 
gouge samples that are commonly used in vertical drilling should be directly 
applicable to gouge sampling in horizontal drilling. ASTM method D- 1587-67 
(AASHTO designation; T207-70) describes the procedure for furnishing 
relatively undisturbed gouge samples using a thin walled sample tube for 
sample collection. Briefly, this method requires the borehole to be clean 
and free of debris. The thin wall tube is placed at the bottom of the hole, 
smoothly pushed into the gouge at the end of the hole, and then twisted two 
revolutions to break off the sample. The sample so obtained must be 
properly sealed and packed for shipment to the testing laboratory. 

The second technique will obtain a reasonably 
undisturbed sample in gouge that is hard enough to prevent the smooth 
insertion of the thin walled sample tube as required by the first method. 
In .this technique, the sample is again collected in a thin walled tube, 



13 8 










_...._ 









: 



33 



The split tube preserves the as -drilled quality 
of recovered core 



Figure 6.56 - Split Tube Core Barrels 
(Courtesy, Christensen Diamond Products) 



11 



6-139 



but insertion of the tube is facilitated by drilling away the gouge outside 
of and just behind the advancing core tube. 

The Osterberg Piston Sampler, manufactured 
and distributed by Soiltest of Evanston, Illinois, is a device specifically 
designed to permit collection of a soil sample in accordance with ASTM 
Method D-1587. It is shown schematically in Figure 6.59(a). The 
sampler, attached to A or AW drill rod, is placed at the bottom of the 
bore hole. Drilling fluid is then pumped down the drill rod to the sampler, 
driving the piston- sampler head into the soil. To free the sample, the 
device is rotated by rotating the drill string and then retracted by pulling 
the drill string out of the hole. It is available in core barrel sizes 
ranging from 2-1/2 inches (64 mm) to 5 inches (127 mm), corresponding 
to overall diameter between 3-3/8 inches (86 mm) and 5-3/4 inches (146 mm). 
For small diameter holes, the sample is obtained by removing the drill 
string, attaching the sampler, sending the drill string back into the hole 
and removing the drill string when the sample has been obtained. The 
device could possible be modified to permit pumping it down the drill string 
on a wireline after a full core barrel has been retrieved. 

The second technique can be implemented using 
the Denison Sampler, Figure 6. 59(b), also available from Soiltest. To 
use the Denison Sampler, the drill string is removed, the sampler is 
attached to the drill string and sent to the bottom of the hole. The 
sampler is rotated and thrusted from the surface. The inner barrel, 
suspended from the outer barrel on ball bearings, advances without rotating, 
collecting the sample core. The outer barrel, being rotated by the drill 
string, cuts away the gouge surrounding the core. Minimal drilling fluid 
circulation during the collection process serves to clear away the small 
chips produced by the rotating outer barrel. The Denison Sampler is 
supplied in outside diameters ranging between 3-1/2 inches (89 mm) and 
7-3/4 inches (197 mm), recovering samples ranging between 2-3/8 inches 
(63 mm) and 6-5/16 inches (160 mm) in diameter. 

The Lowe- Acker improved piston- plug sampler 
might also be employed in gouge sampling from horizontal holes. This is 



6-140 










Figure 6.5 7 - Orienting Core Barrel 

and Scribed Core Sample 

Courtesy, Christensen Diamond Products) 



6-141 



Cores scribed using knives in inner tube shoe. 






(a) 



(b) 



Figure 6.58 - Core Goniometer and Thin Core Sections 



6-142 



mmmmm*. 




»- "• - -Drill rod 

^■-Sampler head- - &.*»* 
JS-S - -Piston 



-Hollow piston ■ 



-Fixed piston — !»« 



HI- Boil check 



-jjijjijj — Air irent 



|-*4 --- - Water under 
pressure 



1 



• — - - Thin moiled — - 
sampling tube 



■-"■-Soil sample — t-- 

OSTERBERG PISTON SAMPLER, NEW MODEL 



(a) 



(b) 



Figure 6.59 - Soil Sampling Device; 
(Courtesy, Soiltest Inc.) 



6-143 



an improved sampler which combines the features of the plug type sampler 
and the stationary piston sampler. This sampler is described as a rugged, 
heavier duty sampler particularly useful in deep sampling of heavy clay. 
This sampler is available from Acker Drill Company, Inc. . 

In considering techniques to sample gouge from 
horizontal holes, organizations involved in soil sampling activities should 
be consulted. A list of such companies is included in Appendix B. Among 
the major concerns involved in manufacturing and /or distributing soil 
sampling equipment are Acher Drill Company, Inc. , Longyear Company, 
and Soiltest, Inc. . 

A study now being directed by Dr. Charles H. Dowding 
of Massachusetts Institute of Technology for FHWA titled, "Determination 
of the Feasibility of Using Horizontal Penetration Techniques for Pre- 
excavation Subsurface Investigation in Soft Ground Transportation Tunnels", 
also addresses the problem of soil sampling in horizontal holes. The 
report of this study should be available by the end of 1975. 

There is also a class of equipment known as side 
wall coring devices which are capable of obtaining disturbed gouge samples 
from considerable depths. One such device, used in the petroleum field, 
obtains core samples by firing steel cups into the hole wall from a gun. 
The cups are held to the gun body with wires and can be retrieved with 
the gun on a wireline. Hunt Tool Co. of Houston, Texas manufacturers 
another type of side wall sampling tool which is illustrated schematically 
in Figure 6. 60. This device can also be run in and out of the hole using 
wireline techniques. However, side wall coring devices have not been applied 
to horizontal drilling. 

In considering techniques to sample gouge from 
horizontal holes organizations involved in soil sampling activities should 
be consulted. A list of such companies is included in Appendix A. Among 
the major concerns involved in manufacturing and /or distributing soil 
sampling equipment are Acker Drill Co. , Inc. , Longyear Co. , and Soiltest, Inc. 



6-144 



A study now being directed by Dr. Charles H. 
Dowding of the Massachusetts Institute of Technology for FHWA titled, 
"Determination of the Feasibility of Using Horizontal Penetration Techniques 
for Preexcavation Subsurface Investigation in Soft Ground Transportation 
Tunnels", also addresses the problem of soil> sampling in horizontal holes. 
The report of this study should be available by the end of 1975. 

6. 7 Water Pressure and Permeability Measurements 

In investigating tunnel alignments it is particularly desirable 
to determine in situ ground water pressure and water permeability. The 
simplest technique for measuring pressure is to shut off the flushing fluid 
pump and measure the pressure on the fluid feed line. This is at best 
a gross measure however, and does not give the pressure at a particular 
point in the hole. Piezometers, such as the Pore Water Pressure Cell, 
available from Terrametric of Golden, Colorado, can be used to measure 
water pressure in drill holes. The following sections present specific 
schemes to perform water pressure and permeability measurements in 
horizontal holes. 

6. 7. 1 Water Pressure Measurement 

To measure the ground water pressure at a 
particular hole depth, the permeable water bearing strata at the location 
of the desired water pressure measurement must be isolated from the 
rest of the hole so the full ground water pressure will be measured. A 
pressure measuring device placed inside the isolated area will then 
provide the desired information. 

Techniques to accomplish this task are illustrated 
using equipment available in the petroleum drilling industry. Basic down 
hole pressure measuring equipment consists of packers to isolate sections 
of the hole and a variety of down hole pressure recording and transmitting 
devices. Although this equipment is designed for use in oil well surveying 
and production monitoring, some of it can be used to provide the desired 
water pressure measurements. 



6-145 





HANGING 


SHOE 


POSITION 


CORING SHOE 


STARTING 


OF SHOE 


ON S!D£WALL 


PENETRATION 


WITH CORE 


TO START 


OF TRUE 


SAMPLE 


CORING 


FORMATION 


COMPLETED 



Figure 6. 60 - Sidewall Coring Tool 



6-146 



The Lynes Sentry is a pressure transducer- 
transmitter supplied with compatible packers and tubing that permit 
assembly of the necessary packers and transducer to isolate the area of 
interest and take the pressure measurement. The pressure sensing - 
transmitting element consists of a Bourdon tube to sense the pressure 
and a device to encode the pressure as an 8 digit binary number which 
is then sent to the surface by wire as a string of pulses representing the 
binary number. The set up as shown in Figure 6.61 is sent down the 
hole on the end of the drill string to set up the pressure measurement. 
The minimum diameter hole for use of this equipment is 3-1/2 inches (89 mm). 

The main disadvantage in using this equipment is 
the cost, since it is designed for the much more exacting task of providing 
long term oil well production monitoring. A considerably less expensive 
system could be assembled from packers used in grouting and the down hole 
"pressure bomb", although modifications would be required. (Figure 6. 62) 

6. 7. 2 Water Permeability Measurement 

A technique for the measurement of the water 
permeability of rock and soil currently exists and is basically performed 
as follows. A short length of the borehole is sealed off and the wall is 
cleaned of all drilling mud and debris. Water is then pumped into this 
sealed section at a constant volume flow rate. By measuring the resulting 
pressure as a function of time and knowing the flow rate, hole diameter, 
and length of sealed section, the permeability of the ground may be 
determined. 

The appropriate equation is 

Q = kAh 
L 

where: Q = the quantity of water flowing 

k = the coefficient of permeability 

A - the cross sectional area involved 

y = the hydraulic gradient (ratio of head loss by friction, 
h, to distance, L, in the direction of flow). 



6-147 



If Q is expressed in cubic centimeters per second, A in square 
centimeters, and pressure gradient in atmospheres per centimeter, the 
unit for permeability is the Darcy. In the petroleum industry the 
millidarcy (.001 Darcy) is more commonly used. 

If Q is expressed in gallons of water per day at 60 F, A in square 
feet, h in feet of water and L in feet, the coefficient of permeability is 
expressed in the Meinger unit. 

Although no off-the-shelf piece of equipment 
exists specifically for this purpose, equipment similar to that described 
for ground water pressure measurement may be used if an outlet is 
provided for pumping water into the zone sealed off by the packers. 
The pressure measurement is, of course, provided by the pressure 
sensor located within the sealed zone. The water flow rate can be 
measured at the surface. (Figure 6.63.) 



6-148 





I 


Tubular 
Encased 


i § 


Conductor 
Wire 


* • 




- 






Either / 1 
Reusable / 
Clamps or / 
Banding \ 
Straps \ 


~^ 


Wire^ 
Protector 





r. 




'» 


["■ 


i 


1 


r 


•.•> 


*> o 

1 


r 






r 


'•*» 


1 




;•> 


1 


r 






v . 


','N 


> 


t 


"•"l 




r 







Fig. 33 
SAMPLE READOUT 

Printed readout of Lynes Pressure 
Sentry System is in the form of pulses. 
Short pulses have a value of one, 
longer pulses a value of zero. Pulses 
shown here read as 010111011. To 
convert to pressure reading, operator 
finds the 010111011 code on conver- 
sion chart and takes corresponding 
pressure reading— 600 psi. 



Figure 6.61 - Lynes Pressure Sentry 
(Courtesy, Lynes, Inc. ) 






6-149 




150 




6-151 



7. Assessment of Horizontal Drilling Systems 

This section assesses the horizontal capabilities of state-of-the-art 
(off-the-shelf equipment, proven procedures) horizontal drilling systems 
and the possibilities for "near term" improvement in horizontal drilling 
capabilities. In determining near term capabilities, the following items 
are considered, (1) equipment which is available on a custom order basis, 
(2) modifications to equipment now used in other applications, and (3) pro- 
cedures which have been developed for vertical and directional drilling 
which appear to offer promise in horizontal drilling applications. 

7.1 Penetration Capability 

7.1.1 State- of- the- Art Capability 

The penetration capabilities of state-of-the-art 
systems can be evaluated by reviewing the capabilities of the various 
drilling techniques presented in Section 6. 1. A graphical representation of 
the penetration capabilities of various drilling techniques as a function of 
hole diameter is presented in Figure 7. 1. These capabilities are 
reviewed in order of increasing diameter in the discussion which follows. 

Diamond wireline core drilling is the closest 
thing to a "developed" technique for long horizontal drilling. However, 
even in this field, holes beyond 1000 ft (305 m) in length are rare. 
The penetration capabilities of diamond coring are assessed at 5000 ft 
(1525 m) for the B size (2.360 in, 60 mm), decreasing to 4,000 ft 
(1219 m) for the N size (2.980 in., 76 mm). It should be noted that 
this assessment is related to diamond core drilling equipment which is 
generally termed mining equipment. There is a class of diamond drilling 
equipment which is used in petroleum drilling, but this equipment has not 
been applied to horizontal drilling. Diamond equipment used in petroleum 
drilling is included in the evaluation of near term capabilities. 



7-1 



(SJ3^9TX[T-[XT' u:l ) 



o 

o 


1 ( 1 


1 1 






o 

o 


LO 








1 




o 




03 






/ 

4) 




m 

o 
o 
o 


o 


M 






.s 






o 


u 












o 


— rt 






0) 








% 




bO \ 


V) & 


> 








•S \ 


T" C 




o 




00 






£'.? 




o 
o 




C! 
•i-i 




u \ 






en 




u 




/ 


Q \ 








« 







i£ a 








60 




4-> 


K! c 








a 

•H 

en 


/ 60 


O 


X 




o 
o 




CO 


h 


/ - 
/ •- • 
/ h 


i— 1 

£ d 










o 
o 
If) 




o 




•tf 


/ ° 


d £i 












O 


/ >^ 


1 * 














/ h 

/ "I 

/ o 

/ ^ 


o 



Q 








O 

o 






2s 


o 




J 






ffi w 


















0} 

d d 


































o £ 












III! 


1 / 1 1 




n 8 






1 





! 

a 



(sstpui) J3;aui-eia 3T°H 



7-2 



Down- hole percussive drilling is suitable for holes 
from 4 - 6 in. (102 - 152 mm) in diameter out to 1000 ft (305 m) in 
length. This technique should be limited to applications in medium to 
hard rock in areas where ground water is not expected. 

An evaluation of the state-of-the-art of horizontal 
down-hole motor drilling is essentially an assessment of the horizontal 
drilling capability of the Dyna-Drill. Based on case histories to date, the 
Dyna- Drill is assumed to be capable of drilling to 2000 ft (610 m) with 
the 1.75 in. (44.5 mm) tool (3 in., 76 ram nominal hole diameter) and 
4,000 ft (1220 m) with the 5 in. (127 mm) tool (6.75 in., 171 mm nominal 
hole diameter). 

In the case of rotary drilling there is a substantial 
discrepancy between what has been accomplished in horizontal drilling 
and what has been accomplished in vertical and- directional drilling. 
The longest vertical holes have exceeded 30,000 ft (9144 m) while 
directional holes beyond 15,000 ft (4572 m) in length are not uncommon, 
whereas the longest horizontal hole appears to have been less than 6,000 
ft (1829 m) in length. Probably the most significant factor in this 
discrepancy is that the market for vertical and directional (up to 70° 
from vertical) holes runs to 30,000 holes and $3.4 billion per year 
while the market for long horizontal holes in rock is too small to be 
documented. On the technical side, the most significant impediments to 
horizontal rotary drilling are that (1) bit thrust must be provided by the 
surface drilling rig, rather than by weighting the drill string and (2) this 
requires that drilling be performed with the drill string in compression 
rather than tension. This in turn leads to buckling problems which 
exacerbate the already substantial problem of transmitting energy from 
the surface rig to the bit. Based upon the assumption that the Koken 
FS400 is ah "available" piece of equipment, the penetration capability 
of state-of-the-art horizontal rotary drilling equipment is assessed as 
5000 ft (1524 m) for a 6.75 in. (171 mm) hole, ranging to ft for a 
12 in. (305 mm) hole. 



7-3 



There is a class of equipment which has been 
developed for boring small utility tunnels beneath streets, highways, 
railways, and other structures where cut-and-cover techniques are not 
practical. A state-of-the-art study of the techniques involved concludes 
that they are suitable for boring holes in rock from 15-72 inches (381- 
1829 mm) in diameter to a length of 500 ft (152 m). 

The preceding discussion is a synopsis of the 
penetration capability of state-of-the-art horizontal drilling equipment 
procedures. The next section discusses what should be possible in 
horizontal drilling if the entire range of available drilling equipment 
and drilling procedures were to be applied to the horizontal drilling 
problem. 

7.1.2 Near Term Capability 

Estimates of present day performance and cost 
characteristics (Section 2.2) show that horizontal drilling is substantially 
cheaper than pilot tunneling for performing horizontal penetrations out 
to 5000 ft (1524 m). There is a strong indication that the penetration 
capability of horizontal drilling can be improved substantially while 
reducing the per foot cost of holes. The following discussion addresses 
the question of increasing the penetration capability of horizontal drilling, 

Given the enormous marketing base for vertical 
and directional rotary drilling in the petroleum industry, it is likely 
that one of the most rewarding routes to improving the capabilities and 
economics of horizontal drilling lies in the direction of adapting proce- 
dures and equipment developed in the petroleum industry to horizontal 
drilling requirements. Fortunately, this appears to be a fertile field 
for development. 

Rotary drilling has evolved as the preferred 
technique for petroleum drilling and is now also widely used in blast- 
hole drilling. Raise boring has evolved from petroleum drilling 



7-4 



procedures to become a widely employed shaft drilling technique. 27 
Raise boring machines offer great promise as horizontal rotary drilling 
machines and have in fact been proposed for this application. 



In general raise boring is performed at angles 
ranging from vertical to 45° from vertical and normal deviations are 
quoted at 0.25° per 100 ft (30.5 m) of depth. 27 This is equivalent to 
a deviation of + 0.44 ft (0.13 m) per 100 ft (30.5 m) of depth. In 1970 
a raise boring pilot hole 12.25 in. (311 mm) in diameter was drilled 
at an angle of 21.5° from horizontal and 405 ft (123 m) in length and 
was described as "right on target at the break-through." Raise 

boring machines differ from petroleum drilling rigs in that they are 
capable of applying thrust to the bit. It is this characteristic of the 
raise boring machine which makes it suitable as a horizontal rotary 
drilling machine. Table 6.6 lists the performance specifications of a 
"small" raise boring machine. Larger units have thrust capacities 
approaching 500,000 lb (226,800 Kg) and torque capacities to 220,000 
ft. lb (30,419 Kg.m). 36 

If raise boring machines can be modified to perform 
as horizontal rotary drilling rigs, and indications at this time are that 
they can, one of the major stumbling blocks to adapting rotary drilling 
procedures to long horizontal drilling can be overcome, that is, finding 
suitable surface rigs. Among the factors which make it attractive to 
adapt rotary drilling to the problem of horizontal drilling in rock, some 
of the more significant are the following: 

(1) As the preferred technique for petroleum drilling, rotary 
drilling is by far the most well developed drilling method 
in terms of equipment and procedures. 

(2) Rotary drilling methods are suitable for the entire range 
of formation strengths from very soft to very hard. 



7-5 



(3) Rotary drilling has proven to be the most economical 
method of drilling long holes in rock. 

(4) The larger hole sizes which are compatible with rotary 
drilling equipment are more conducive to maintaining a 
straight hole. The reason for this is that the ability of 
the drill string assembly to drill straight increases with, 
its stiffness, and the stiffness of the string is proportional 
to the fourth power of its diameter. 

With the proper surface rigs, and employing roller 
or non- rotating stabilizers spaced along the entire drill string, to pre- 
vent buckling and reduce friction between the drill string and hole wall, 
rotary drilling methods should be capable of penetrations well beyond 
present limits. Holes to 10,000 ft (3048 m) and beyond and diameters 
from 7-15 inches (178 - 381 mm) do not seem unreasonable. 

With larger surface rigs, diamond full- hole and 
core bits developed for the petroleum industry could be used for hori- 
zontal drilling. This would allow diamond wireline coring up to 12.25 in, 
(311 mm) in diameter with cores to 5.25 in. (133 mm) in diameter and 
full hole diamond drilling to 12.5 in. (318 mm) in diameter. The reduced 
thrust and torque requirements for diamond bits (relative to equal outside 
diameter rolling cutter bits) should allow longer penetration capabilities, 
for a given hole size, with diamond bits. However, bit costs per foot 
would be greater than for rolling cutter bits. 

Down- hole motor drilling is not an economical 
method of straight hole drilling in most circumstances in petroleum 
drilling, and it does not seem likely that the economics of down-hole 
motor drilling will be more attractive in horizontal straight hole drilling. 
However, the down-hole motor is a strong candidate for extending pene- 
tration capabilities beyond what is achievable with techniques which 
require that the drill string be turned. The technique has been pro- 
jected as suitable for distances to 15,000 ft (4572 m) by some sources. 

Down- hole percussive diilling should be applicable 
out to 1,000 ft (305 m) for the range of available equipment. This would 
allow hole diameters to 12 inches (305 mm). 

7-6 



The projected horizontal penetration capabilities for 
systems which would adapt available equipment and procedures to hori- 
zontal drilling are presented in Figure 7.2. 

7.2 Chip Removal 

It is highly unlikely that anything other than drilling mud 
will be used as a flushing fluid in a developed procedure for long 
horizontal drilling. (For distances beyond 1,000 ft, 305 m) The ability 
of drilling mud to control lost circulation, stabilize the hole, and 
lubricate the drill string to hole wall interface is essential to a success- 
ful horizontal drilling operation. 

In future programs, double tube reverse circulation may 
be used in certain circumstances to control lost circulation. 

7.3 Hole Stabilization 

The stabilization procedures presented in Section 6.3 are 
capable of controlling most hole stabilization problems. However, based 
on the experience of drilling contractors, there will be instances where 
casing will have to be employed or the hole will have to be abandoned. 

With the application of equipment which would allow larger 
hole sizes, the procedure of inserting plastic or fiberglass pipe inside 
the drill string (see Figure 6.27) becomes increasingly viable as a non- 
metallic casing technique, in that the resulting final hole diameter 
assumes more useful proportions. 

7.4 Guidance 

7.4.1 State- of- the- Art 



State-of-the-art survey tools are limited to magnetic 
single shot and multi-shot devices. Steering techniques which are 



7-7 









(£ 


JL313U1THXUJL) 








o 


1 1 1 


1 1 


« 1 1 1 1 | 1 


o 








o 


■~~ 






in 






- 


o 




i 


1 - 


o 

lO 


— 




K 


<* 






\ 


o 






\ 


o 






\ 


o 






\ - 


■* 






\ 


o 






o 5i \ 


o 
in 






ffi A v 


CO 






d a A 

5' A 


o 
o 


CD 




1$ A 


o 

CO 


| 




\. j \ 




o 






o 
o 


2 




X \ 


LD 






o 
o 
o 


1 
g Boring 

Boring 


Rotary 

d Coring 
Full 


\ : 


o 
o 
m 


_ a ; 


3 


' d 
1 o 

• ni 

1 Q 


^ ■ 




T3 






\ 






d 








i ■" 


o 


o 










o 


_ tf 










o 
















1 


i 


















i! 




! 


1 










Ij 










9ATSST1 


DJScJ 












9XOH- 


UM.OQ 


!. 




1 1 


l 1 


1 1 


1 1 


1 


1 1 1 



_ f> 



^ 


o 




o 




o 




^H 


o 


■ — ' 




rd 








ft 


a; 


0) 




Q 


r- 


CD 




O 




£ 



(S9t[3Ul) ja^atu-BTQ 9X°H 



7-8 



effective in drilling rock are limited to (1) techniques employing the 
fulcrum principal, (2) whip stocking and (3) the Dyna- Drill. The best 
estimate of the guidance capabilities of this combination of techniques 
is portrayed graphically in Figure 7.3. 

One factor which adds greatly to the expense and 
time involved in horizontal guided drilling is the necessity for frequent 
corrections of the drilling trajectory. Instances have been reported 
where whipstocking was employed at 10 ft (3.05 m) intervals to maintain 
a trajectory within 15 degrees of the desired trajectory. By contrast, 
the procedures employed in directional drilling for the petroleum industry 
most often involve (1) employment of a down-hole motor to achieve an 
initial deviation from vertical, (2) buildup of the deflection through use 

of the fulcrum principal, and (3) drilling to completion in a straight 

32 
line with a drilling assembly employing a high degree of stabilization. 

The final straight hole leg can be up to 70 degrees from the vertical. 
The factor which allows the directional driller to hold a reasonably 
straight course is the stiffness of the drill string immediately behind 
the bit. The smaller diameter (B size) equipment employed in most 
state-of-the-art long horizontal drilling does not have the stiffness re- 
quired to resist hole deflecting factors. 

A second significant state-of-the-art limitation is 
the lack of high angle survey steering tools. In petroleum drilling, the 
availability of the survey steering tool has made the down- hole motor 
the most frequently used deflection tool. With this instrument the 
driller can correct for the drill string torque reaction, and achieve the 
exact angular orientation required for the down- hole motor. The hori- 
zontal driller must drill a length of hole with the down- hole motor and 
then run a survey instrument down the hole and retrieve it, to determine 
if he made proper allowance for the drill string torque reaction. 



7-9 



(SJtO^Otu) 









1 i I 






1 
















4J 




o 

o 


_ o 

CO 


^ 




1—1 




o 


















o 


— IT) 


+-> 




LP) 




> 

CD 






Q 




o 


ir> 


«j 




U"> 


™* r-H 


u 






' — ' 










^1 




o 


o 


d) 




o 


~ CO 


> 










o 








o 


~ ^£, 






o 
un 

o 

o 


Co 

CO 


I 
£ 




o 
in 


- m 


a 


L____^ °^ ^\^ 






o 


^'^^^ __^^ 




> 








a) 




o 


LD 


Q 








n! 




o 


o 






o 


_ co 


fl 




rH 




O 












o 


vD 


•H 




in 


- ^ 


o 




1-4 




X 




o 


^ 






o 

CV3 


" sO 




! 1 S 1 



o 


o 


o 


o 


o 


o 


IT) 


^ 


CO 



1£ «q;Suo' T 9io H 



7-10 



7.4.2 Near Term Capability 

Available custom gyroscopic survey equipment will 
improve survey accuracy by about one order of magnitude. The avail- 
ability of high angle survey steering tools will make the down- hole motor 
the preferred deflection tool for horizontal drilling. This in turn, will 
reduce the time required to make direction changes. The net result 
of applying this equipment horizontal drilling should improve guidance 
capability to + 1 ft (0.3 m) per 1,000 ft (305 m) drilled in terms of 
survey accuracy, with a steering capability of + 5 ft (1.5 m). This 
capability is illustrated graphically in Figure 7.3. 

The use of rotary and diamond drilling equipment 
in large diameters will allow more effective stabilization of the drill 
string behind the bit. ■ This should increase the interval required between 
corrections in hole trajectory. 



7-11 



8. Planning and Estimating Horizontal Drilling 

8. 1 Selecting a Drilling Technique 

In contemplating the use of horizontal drilling as a tech- 
nique for exploring along proposed tunnel alignments, the options 
available, in terms of state-of-the-art equipment, are quite limited. 
If coring is required along the entire alignment, then diamond wireline 
coring is the only technique available. If intermittent coring is 
acceptable, then rotary drilling, down -hole motor drilling, and down- 
hole percussive drilling are candidate techniques. Requirements in 
terms of hole diameter and hole length further restrict the available 
techniques as indicated in Figure 7.1. Down-hole percussive techniques 
are limited to competent formations of medium to hard rock with minimal 
ground water. A logic diagram for determining the available options 
in selecting a drilling technique is presented in Figure 8.1. It should 
be noted that if rotary drilling is to be employed, a modified raise 
borer, road boring machine, or blasthole rig will probably have to be 
used as a surface rig. 

8. 2 Horizontal Drilling as a Development Program 

If the horizontal drilling customer is willing to fund 
developvnental work on a horizontal drilling program, significant areas 
for investigation should include: 

(1) Complete instrumentation of the drilling 
system to record thrust, torque, rotational 
speed, penetration rate etc. 

(2) Development of a rotary drilling surface rig 
to allow the application of the complete range 
of rotary drilling techniques to horizontal 
drilling. 



8-1 



Less than 
3 inches 
(76 mm) 



Is Continuous Coring 
Required? 



<j> 



What is the desired 
hole diameter? 



Less than 6. 75 
inches (172 mm) 



Greater than 
6. 75 inches 
(172 mm) 



What is the desired 
hole length? 



Less than 1,000 feet 
(305 m) 



Diamond wireline 
core drilling is 
feasible 



Downhole 
percussive 
drilling is 
feasible 



Greater than 1,000 feet 
(305 m) 



Downhole 
motor 
drilling is 
feasible 



Rotary drilling 
is feasible 



Figure 8. 1 - Drilling Method Selection Process 



8-2 



(3) Evaluation of available custom order high 
angle survey steering tools. 

(4) Evaluation of available custom order gyroscopic 
survey tools. 

(5) Development of automated rod handling systems. 

(6) In conjunction with (2), evaluation of drill 
string stabilization techniques. 

8. 3 Costing Model 

Volume II of this report is a Long Hole Horizontal 
Drilling Cost and Time Requirements Estimating Manual. The manual 
presents a method for determining the time and co«t required to drill 
a horizontal hole by any of four methods : 

(1) Diamond Wireline Core Drilling 

(2) Rotary Drilling 

(3) Down -Hole Motor Drilling 

(4) Down -Hole Percussive Drilling 

Relationships were developed for determining the time 
required for each drilling activity. These relationships include all 
variables which affect the total time required. Values for these 
variables were determined from (a) analytical techniques, where such 
techniques were available, (b) consultation with drilling contractors, 
(c) empirical data, where available. The technique or combination of 
techniques employed to determine the value of variables or rules -of- 
thumb to be employed are indicated in the model. 



8-3 



The primary value of this model is to establish logical 
techniques for defining the governing parameters in horizontal drilling. 
The accuracy of the model as a method of predicting drilling costs 
will improve as the quality of available data improves. Diamond wire- 
line core drilling is the only technique for which there is any sort of 
data base in horizontal applications. For this technique, the model 
predictions correlate well with contractor field data and estimates. 



8-4 



APPENDIX A 
EQUIPMENT MANUFACTURERS AND CONTRACTORS 



This appendix lists representative manufacturers of drilling 
equipment and experienced horizontal drilling contractors. The numbers 
refer to the alphabetical company listing contained in Appendix B. This 
is not intended to be an exhaustive listing. Further listing of equipment 
manufacturers and drilling contractors may be obtained from: 

Composite Catalog of Oil Field Equipment and Services , Gulf 
Publishing Company, Houston, Texas. 

Petroleum Industry Yellow Pages, Whico/ General Telephone 
Directory Co., Houston, Texas. 



A. Manufacturers - Drill Rigs 



1. Diamond: 

1, 6, 8, 10, 26, 30, 47, 48, 49 

2. Rotary: 
28 

3. Down -Hole Motors: 
13, 15, 16, 18 

4. Down-Hole Percussive Drills: 
1, 25, 34, 37 

5. Raise Boring Machines: 
25, 33, 40 

6. Road Crossing Boring Machines: 
35, 39 



A-l 



B. Manufacturers - Drill Bits 

1. Diamond: 

1, 6, 9, 10, 30, 47, 51 

2. Rolling Cutter: 

1, 20, 30, 33, 36, 42, 51, 56 

3. Percussive: 

1, 20, 37, 51 

C. Contractors - Drilling 

5, 7, 8, 30, 38, 41, 44, 47 

D. Manufacturers and Service Companies - Drilling Mud 

4. 11, 32 

E. Manufacturers and Service Companies - Grouting 
11, 19 

F. Manufacturers and Service Companies - Hole Surveying 
16, 23, 29, 43, 46 

G. Manufacturers - Stabilizers, etc. 
2, 12, 14, 16, 21, 24 

H. Manufacturers - Steering Tools 

2, 15, 16 

I. Manufacturers and Service Companies - Fishing 

2, 11, 20, 21, 24, 27, 30, 50, 52, 53, 54, 55 



A-2 






J. Manufacturers and Service Companies - Core Sampling 

1. Core Barrels, etc. 
1, 5, 9, 30 

2. Oriented Core. 
9, 16, 41 

K. Manufacturers - Soil Sampling 

17, 24, 30, 45, 47 

L. Manufacturers - Water Pressure and Permeability Measuring 

Components 

3. 17, 29, 31 



A-3 



APPENDIX B 
ADDRESS LISTING 

This appendix lists alphabetically the names and addresses of 
the companies referred to in Appendix A. The numbers refer to the 
equipment and contractor categories used in Appendix A. 



1. Acker Drill Company, Inc. 
Box 830 

Scranton, Pennsylvania 18501 

Phone: 717-586-2061 

Al, A4, Bl, B2, B3, Jl, K 

2. A-Z International Tool Co. 
3317 West 11th Street 
Houston, Texas 77008 
Phone: 713-869-6451 

G, H, I 

3. Baker Division 
Baker Oil Tools, Inc. 
7400 E. Slauson Avenue 
P.O. Box 2274 

Los Angeles, California 90051 

Phone: 213-724-5400 

L 

4. Baroid- Division, NL Industries, Inc. 
P.O. Box 1675 

2402 Southwest Freeway 
Houston, Texas 77001 
D 

5. Boyles Bros. Drilling Company 
P.O. Box 58 

1624 Pioneer Road 

Salt Lake City, Utah 84110 

Phone: 801-487-3671 

C, Jl 

6. Boyles Operations, Dresser Industrial Products Ltd. 
256 Hughes Road 

Box 460 

Orillia, Ontario L3V6K3, Canada 

Phone: 705-325-6131 

Al. Bl 



B-l 



7. Calvert Western Exploration 
Box 2920 

Grand Junction, Colorado 81501 

Phone: 303-242-4124 

C 

8. Canadian Mine Services 
745 Clark Drive 

Vancouver, British Columbia V5L3J3, Canada 
Al, C 

9 Christensen Diamond Products Company 

193 7 South 300 West 
P.O. Box 387 

Salt Lake City, Utah 84110 
Phone: 801-487-5371 
Bl, Jl, J2 

10. Craelius S.A. 
F-06 

Carros Industries, France 
Phone: (93) 08.13.21. 
Al, Bl 

11. Dowell Schlumberger 
909 Americana Building 
Houston, Texas 77002 
Phone: 713-224-1313 
D, E, I 

12 Drilco Division of Smith International, Inc. 

P.O. Box 3135 
Midland, Texas 79701 
Phone: 915-683-5431 
G 

13. Drilling Tool Division of Cook Testing Co. 
2552 Cherry Avenue 

P.O. Box 6127 

Long Beach, California 90806 

Phone: 213-426-3031 

A3 

14. Driltrol 

1361 East Hill Street 

Long Beach, California 90806 

Phone: 213-424-0461 

15. Dyna-Drill Co., Division of Smith, International, Inc. 
P.O. Box 327 

Long Beach, California 90801 
Phone: 213-426-7186 
A3, H 



B-2 



16. Eastman Whipstock Inc. 
P.O. Box 14609 
Houston, Texas 77021 
Phone: 713-748-2350 
A3, F, G, H, J2 

17. Gearhart-Owen Industries, Inc. 
P.O. Box 1936 

Fort Worth, Texas 76101 
Phone: 817-293-1300 
K, L 

18. Grant Oil Tool Company 
(Neyrpic turbodrills) 
2042 East Vernon Avenue 

Los Angeles, California 90058 

Phone: 213-232-8167 

A3 

19. Halliburton Services 
Drawer 1431 

Duncan, Oklahoma 73533 
Phone: 405-255-3760 
E 

20. Hendershot Tool Company 
1006-12 S.E. 29th Street 
P.O. Box 94444 

Oklahoma City, Oklahoma 73109 

Phone: 405-677-3386 

I 

21. Homco International, Inc. 
P.O. Box 2442 
Houston, Texas 77001 
Phone: 713-734-0281 

G, I 

22. Hughes Tool Company 
Oil Tool Division 

P. O. Box 2539 
Houston, Texas 77001 
Phone: 713-926-3101 
B2, B3 

23. Humphrey Inc. 
2805 Canon Street 

San Diego, California 92106 

Phone: 714-223-1654 

F 



B-3 



24. Hunt Tool Company 
P.O. Box 1436 
Houston, Texas 77001 
Phone: 713-223-7131 
G, I, K 

25. Inge r soil -Rand Co. 

Woodcliff Lake, New Jersey 07675 
Phone: 201-887-1212 



Memorial Parkway 
Philipsburgh, New Jersey 
A4, A5 

26. Joy Manufacturing Co. 
Claremont, New Hampshire 03743 
Al 

27. Joy Oil Tools 
Baash-Ross Division 
P.O. Box 1348 
Houston, Texas 
Phone: 713-672-1721 
I 

28. Koken Boring Co., Ltd. 
Taira-cho 2-20-13, Meguro-ku 
Tokyo, Japan 

Phone: 717-1141 
A2 

29. Kuster Company 
2900 East 29th Street 

Long Beach, California 90806 
Phone: 213-426-9311 

F, L 

30. Longyear Company 

925 Delaware Street S.E. 
Minneapolis, Minnesota 55414 
Phone: 612-331-1331 
Al, Bl, B2, C, I, Jl, K 

31 . Lynes, Inc. 
7042 Long Drive 
P.O. Box 12486 
Houston, Texas 77017 
Phone: 713-643-4393 
L 



B-4 



32. Magcobar Operations 

Oil Products Division of Dresser Industries, Inc. 
P.O. Box 6504 
Houston, Texas 77005 
D 

33. Mining Equipment Operation 

Mining Services and Equipment Division of Dresser Industries, Inc. 
P.O. Box 24647 
Dallas, Texas 75224 
A5, B2 

34. Mission Manufacturing Co. 
P.O. Box 40402 
Houston, Texas 77040 
A4 

35. PCM Division of Koehring Co. 
Port Washington, Wisconsin 53074 

A6 

36. Reed Tool Co. 

Drilling Equipment Division 
P.O. Box 2119 
Houston, Texas 77001 
B2 

37. Reed Tool Co. 

Rotary Percussion Equipment Division 

P.O. Box 3641 

San Angelo, Texas 76901 

A4, B3 

38. Reynolds Electrical and Engineering Co., Inc. 
P.O. Box 14400 

Las Vegas, Nevada 89114 

Phone: 702-734-3011 

C 

39. Richmond Manufacturing Co. 
P.O. Box 588 

Ashland, Ohio 44805 
Phone: 419-869-7107 

A6 

40. James S. Robbins and Associates, Inc. 
500 Wall Street 

Seattle, Washington 98121 
Phone: 206-767-7150 
A5 



B-5 



41. Charles S. Robinson & Assoc. 
622 Gardenia Court 

Golden, Colorado 80401 
Phone: 303-279-0028 
C, J2 

42. Rucker Hycalog 
P.O. Box 15372 
Houston, Texas 77020 
Phone: 713-675-8221 
B2 

43. Scientific Drilling Controls, Inc. 
4040 Campus Drive 

Newport Beach, California 92660 
Phone: 714-557-9051 

F • 

44. Soil Sampling Service, Inc. 
5815 North Meridian 
Puyallup, Washington 98371 
Phone: 206-927-3173 

C 

45. Soiltest, Inc. 
2205 Lee Street 
Evanston, Illinois 60602 
Phone: 312-869-5500 

K 

46. Sperry-Sun 
P.O. Box 36363 
Houston, Texas 77036 
Phone: 713-494-3021 

F 

47. Sprague and Henwood, Inc. 
221 West Olive Street 
Scranton, Pennsylvania 18501 
Phone: 717-344-8506 

Al, Bl, C, K 

48. Tigre Tierra, Inc. 
5815 North Meridian 
Puyallup, Washington 98371 
Phone: 206-927-7411 

49. Tone Boring Machine Mfg. Co. 
Tokyo, Japan 

Al 



B-6 



50. Tri-State Oil Tool Industries, Inc. 
P.O. Box 5757 

Bossier City, Louisiana 71010 
Phone: 318-746-3800 

I 

51. Varel Manufacturing Co. 
9230 Denton Drive 
P.O. Box 20156 
Dallas, Texas 75220 
Phone: 214-351-6487 
Bl, B2, B3 

52. Wilson Industries, Inc. 
P.O. Box 1492 
Houston, Texas 77001 
Phone: 713-225-4071 

I 

53. Bowen Tools, Inc. 
P.O. Box 3186 
2429 Crockett Street 
Houston, Texas 77001 
Phone: 713-869-6711 
H, I 

54. The Dia-Log Company 
Box 14103 

Houston, Texas 77021 

I 

55. Houston Engineers, Inc. 
P.O. Box 567 

1710 Burnett Street 
Houston, Texas 77001 
Phone: 713-227-4188 
I 

56. Smith Tool. Co. 

Division of Smith International, Inc. 

P. O. Box 4549 

Compton, California 90224 

Phone: 213-324-4977 

B2 



B-7 



APPENDIX C 



GROUTING 



The following material was prepared by Jacobs Associates of 
San Francisco, California. Included is a detailed discussion of grouting 
and an assessment of the impact of grouting procedures on hole cost. 
The economic data was based on the "Estimating Manual for Time and 
Cost Requirements" which constitutes Volumell of this report. 

C.l. Drill Hole Stabilization 



Other than steel casing, which is not recommended for this study, 
grouting appears to be the most promising method of horizontal drill hole 
stabilization. Particular drilling parameters, s uch as hole diameter and 
drilling fluid, may be dictated by the method of stabilization selected. 

Where grouting is employed as a stabilization medium it would be 
preferable to use water, rather than mud, as a drilling fluid. The use of 
mud may create additional grouting trips and a resultant time delay. Drilling 
mud forms an impervious layer on the hole walls, which may interfere with 
a grouting operation. Figure C. 1. (a) shows the cross section of a hypothetical 
drill hole with an impervious mud layer on the walls and a failure, due to 
high groundwater pressure, at the top of the hole. Figure C. 1. (b) shows 
the same section after a grouting operation. The grout was unable to 
penetrate the impervious mud layer which resulted in a partial grouted 
section around the hole. High water pressure then collapsed another portion 
of the hole which required an additional grouting operation. The same hole 
section drilled with water as a drilling fluid is shown in Figure C. 1. (c). 
Absence of a layer of impervious mud permitted a full grouted section in 
one grouting operation. 

Hole size is another important consideration when hole stabilization 
activities are required. Small diameter holes are generally more self 
supporting than large holes and they require less grout when grouting is 
necessary. 



C-l 



Impervious Mud 
Layer 



Partial Grouted 
Section 



Full Grouted 
Section 








New Failure 



(a) 



(b) 



(c) 



Figure C. 1 - Effect of Drilling Fluid on Grouting Activities 



C-2 



The typical method of grouting drill holes is with a cement water 
grout. This grout usually has a 6 to 1 water to cement ratio and is 
pumped to a resistance pressure-as high as 3000 psi. This method may 
require great volumes of grout to be pumped into a formation before a 
cement filter plug is acquired. A cement filter plug will occur in fissures 
of 0. 25 mm. or less. Grout may be pumped great distances before meeting 
this condition. , ,. ._ . r . 

Other disadvantages to neat cement grout are set volume reduction 
and the time required to attain adequate strength to continue drilling. 
Grout with a 6 to 1 water to cement ratio may have a set volume reduction 
up to 75%. This condition, in conjunction with high water pressures may 
cause cement plugs to be forced out of the fissures and a resulting drill 
hole collapse. Forty eight hours or more may be required for cement 
grout to attain adequate strength for drilling to continue. Delays of this 
nature can be very -costly, particularly when frequent grouting operations 
are required. *» 

C. 2. Characteristics and Conditions for Grouting Drill Holes 

For successful, economical, drill hole grouting the following character- 
istics and conditions must be met. 

a) Grout must have a predictable, controllable, set time. The 
set time should be controllable from a few seconds to several 
minutes. 

b) Full volume set is required and a small amount of set 
expansion is desirable. 

c) The material must have adequate strength for prevailing 
conditions. 

d) It must have the ability to penetrate the voids and fissures 
encountered. 



C-3 



e) Grout chemistry must be compatible with the formation. 

f) Temperature changes in the formation must be monitored 
to assure accuracy of set times. 

All of the above conditions can be met by one or more of the 
available grouting materials provided there is adequate confining pressure 
in the formation. It may not be possible to grout drill holes, in soil, 
close to the surface. If more than 15% of the material passes a 200 mesh 
and 100% passes a 1/4 mesh the formation will probably not offer adequate 
confining pressure. 

C. 3. Grouting Materials 

Grouting materials available for stabilizing drill holes may be 
classified as particulate and chemical grouts. Particulate grouts have 
particles in suspension. The most commonly used particles are cements, 
bentonite and flyash. Chemical grouts are solutions and they contain no 
particles. 

These grouts have wide variations in gel times, viscosites, strengths 
and costs. Any one of the grouts may have advantageous properties for a 
particular application. Table C. 1 lists some particulate and chemical grouts 
that are commercially available. 

High viscosity grouts, generally, have a higher unconfined com- 
pressive strength than low viscosity grouts. However, fine fissures and 
voids may not always be penetrated by high viscosity grouts. Cement 
grouts have unconfined compressive strengths up to 75, 000 psf. Bentonite 
may be added to cement grout to increase viscosity and provide for a full 
volume set. The addition of bentonite retards the set and therefore, 
without a reagent, it is not very satisfactory for grouting drill holes. 
CemChem is a patented process which incorporates a reagent with cement 
bentonite grout. The added reagent makes the grout set time predictable 
and controllable. 



C-4 



TABLE C. 1 
COMMERCIALLY AVAILABLE PARTICULATE AND CHEMICAL GROUTS 

Particulate Grouts 

a) Bentonite 

b) Cement 

c) Cement, Bentonite 

d) Cement, Bentonite and Reagent (CemChem) 

e) Chemical Grouts with Particulates Added 

f) Asphaltic Emulsions 

Chemical Grouts 

a) Acrylic Resin 

b) Chrome Lignin 

c) Poly Phenol 

d) Single Shot Silicates 

e) Two Shot Silicates 

f) Urea Resin 

g) Epoxy Resin 

h) Phenolic Resin 

i) Polyester Resin 



C-5 



Most chemical grouts have lower viscosities than particulate grouts. 
Acrylic Resin is the lowest viscosity grout sold commercially. It has a 
viscosity of 1. 2 centipoises. Chrome Lignin, Poly Phenol and Single Shot 
Silicates have viscosities ranging from 2 to 7 centipoises but they are 
generally used with viscosities of 4 to 5 centipoises. It is more desirable 
to use higher viscosity chemical grouts since they result in higher com- 
pressive strengths. Wetness of a chemical grout is a factor to be 
considered. Wetness may be increased by adding surfactants. This permits 
a high viscosity grout to be used, where a low viscosity would normally be 
used, with no apparent decrease in penetration. Urea Resin, Two Shot 
Silicates, Epoxies and Polyesters are generally used with viscosity ranges 
from 10 to 3 centipoises. All chemical grouts provide a full volume set. 

C. 4 Strength of Grouts 

In general particulate grouts provide high strength for a comparatively 
low cost. Bentonite is an exception since it has insignificant compressive 
strength. Strengths of chemical grouts generally increase with increasing 
viscosity. Low viscosity chemical grouts (2 to 6 centipoises) have very low 
strength when gelled in a container. They are nothing more than a weak 
glue. However in a sand formation unconfined compressive strengths may 
reach 20,000 psf. High viscosity grouts (10 to 30 centipoises) have 
compressive strengths, in sand, of 20, 000 to 75,000 psf. Table C. 2 lists 
the unconfined compressive strengths of fome grouts. 

Time for grout to attain adequate strength, to permit drilling to 
resume, is an important economic factor. Grout cure times may vary 
anywhere from a few minutes to seven or eight clays. If no groundwater 
pressure exists, neat cement grout may be drilled through within a few 
hours. However, there is a great danger of washing out the grout with 
drilling fluid and recreating lost circulation. On the other hand, if high 
groundwater pressure exists, it may be necessary to wait two to eight 
days before drilling through neat cement grout. 

Two shot silicates acquire their full strength almost immediately. 



C-6 



TABLE C. 2 



UNCONFINED COMPRESSIVE STRENGTH OF GROUTS 



Grout Type 



Unconfined Compressive Strength Approximate Cost 
in P. S. F. per Gallon $ 



Bentonite 

Cement 

CemChem 



Insignificant 

75, 000 

20,000 to 30,000 



0.30 
0.45 



Acrylic Resin 
Chrome Lignin 
Poly Phenol 
Single Shot Silicates 



4,000 to 20,000 



0. 15 to 1. 50 



Two Shot Silicates 
Urea Resin 
Phenolic Resin 



20,000 to 75,000 



0. 50 to 1. 50 



Epoxy Resin 
Polyester Resin 



5. 00 to 3 0. 00 



TABLE C.3 



GROUT CURE TIME 



Grout Type 

Neat Cement 

Cement Bentonite & Reagent 

Chemical Grouts 



Cure Time 

3 hours to 8 days 
1/2 to 1 hour 

to 48 hours 



C-7 



Cement bentonite and reagent grout (CemChem) also has a very short cure 
time. Approximate ranges of cure times are shown in Table C.3. 

C. 5 Cost of Grouting Materials 

Cement grouts and some chemical grouts have a relatively low cost. 
Several of the chemical grouts are very costly. Approximate costs of some 
grouting materials are shown in Table C. 2. 

C. 6 Grouting Equipment 

Equipment required for a grouting activity varies with the type and 
method of grouting. In general two grout pumps, two mixing tanks and 
material storage tanks are required. The cost of the required equipment 
can vary from $10,000 to $25,000. 

C. 7 Selection of Grouts and Methods of Grouting 

The most important factor in the selection of grouts is that they are 
capable of performing the required function. A secondary but important 
factor is low overall cost. In most drill hole applications there is very 
little knowledge of void ratios, fissures widths or groundwatei pressure. 
Without the above knowledge a logical approach would be to estimate an 
amount of grout to provide a grouted radius of 2 to 5 feet around the hole. 

Because of its low cost, moderate strength and short curing time, 
a cement bentonite • and reagent grout would be a good first election, '-he 
grouted section could be drilled through withr'n an hour and its adequacy 
determined. In the event that adequate penetration was not accomplished 
the hole could then be grouted with a high viscosity chemica ^rout. This 
could be followed by an application of low viscosity grout, if adequate 
penetration was still not achieved. 

C. 8. Economic Considerations 



To show the economic impact of various drill hole grouting selections, 
a sample hole is evaluated, using neat cement grout Classical grouting method), 
cement bentonite and reagent grout and a high viscosity chemical grout. The 
requirements, assumptions and estimates used for the sample hole are listed. 
Some additional estimates are also included. 

(1) Hole lengths of 1, 000 through 5, 000 feet 

(2) Method of drilling^ selected is NQ (approximately 3 inches 
diameter) wireline coring 

(3) Maintain the hole within a + 1% deviation 

(4) An average geological profile is assumed 

(5) An average bit life of 120 feet 

(6) Penetration rates of 8, 18, and 3 feet per hour for hard, 
medium and soft rock respectively 

(7) A direction change every 90 feet to maintain alignment 

(8) A hole survey every 3 feet and three additional hole surveys 
ev^ry 90 feet for. direction changes 

(9) A fishing activity, every 300 feet 

(10) A hole stabilization activity every 200 feet and a length of 
18 feet for each stabilization activity 

(11) A jobj efficiency factor of (0.2) (time) 

(121 Average drill rod trip velocity of 20 feet per minute. 



C-9 



Tables C. 4 and C. 5 show additional estimates for hole stabilization, 
assuming moderate to high groundwater pressure. ' 

TABLE C. 4 



GROUT CURE TIME 


AND COST 


ESTIMATE 


Grout Type 


Cure Time 
(Hours)* 


Cost $ 
Per Gallon 


Neat Cement 


24 


0.3 


Cement, Bentonite and Reagent 


1 


0.45 


Chemical Grout 


1 


1.00 



*Time required to attain adequate strength for prevailing conditions. 
TABLE C. 5 

GROUT QUANTITY ESTIMATES. 

Cement 
Neat Cement Bentonite Chemical 

Grout Si Reagent Grout 

Estimated Quantity of 

Grout Required Per 

Activity (gallons)* 10,400 2,600 2,600 

Grout cost per Activity ($) 3,120 1,170 2,600 

*Based on providing a grouted radius of 5 feet around the drill hole 
in crushed rock with 25% voids. Since it is not possible to control 
the set time of neat cement grout, a conservative estimate is that 
four times the quantity would be required. 

A summary of time estimates for hole lengths of 1, 000 through 
5,000 feet is shown in Table C. 6. This summary is based on procedures 



C-10 



and formulas outlined in the Cost Model Volume of this study. A 
comparative summary of costs to drill the example hole is shown in Tables 
C.7, C. 8, C. 9 and C. 10 and the results are plotted in Figure C. 2. In this 
summary hole stabilization is accomplished using: 

(a) Neat cement grout 

(b) Chemical grout 

(c) Cement, Bentonite and Reagent grout 

(d) No hole stabilization required 

This economic analysis is very approximate and is only as accurate 
as the idealized conditions are accurate in representing the actual conditions 
in the field. Despite these shortcoming, this analysis leads to two important 
conclusions: 

The first is that hole stabilization can be the most important econo- 
mic factor in drilling long horizontal holes. It can be seen from Figure C. 2 
if hole stabilization is required, the total cost to drill a hole can be more 
than doubled. 

The second conclusion is that the cost can be nearly doubled if an 
incorrect assessment of conditions or a poor selection of grouting methods 
and materials is made. 



C-ll 



4> 




O 


o 


01) 




o 


vO 


<tf 




o 


cr- 


V 




in 




K 








08 




O 


o 






O 


o 


a) 




o 


vO 






•^ 




•H 


■*-> 






c 


3 












o 


r- 


£ 


!-i 


o 


^ 


(L> 


a 


o 


■* 


CQ 


i— i 


CO 




C 





O 


t> 


0) 


a 


o 
o 




0> 


(M 




cu 


rti 






U 


u 


O 


00 




O 


o 


, . , , 


O 


•—i 


■- 1 


(M 


"-< 







o 


O 


co 
m 

i— i 


vO 


o 

vO 


o 

CO 


o 

o 

I— 1 


o 
^f 1 


CO 


sO 

co 


o^ 


t\] 


O 


o 


00 





o 


o 


<tf 


O 


O 


00 


o 


fM 


00 


o 


CO 


■4-> 




o 


vO 


O^ 


O^ 


r- 


in 


r- 


^r 


rg 


r- 


CO 


f-t 




o 


o 






o 


f-t 


co 


i— i 


sO 


r- 




_,_, 


tn 














CO 




■CO 


— 1 


a 
























05' 
93 


o 


o 


o 


"* 


o 


© 


o 


00- 


r\l,- 


^ 




o 


o 


o^ 


vO 


sO 


CO 


o 


Si. 


pj 


^f 


m 




o 


vO 






vO 


1—1 . 


O" 


t ro ' 


■* 


vO 




T) 


■J 


^ 














' c\j 




f\J 


i— i 


«3 


d 










[■ 














nJ 


0) 

a 


o 


r- 


o 


vO 


^ 


o^ 


m 


H ' 


■oo 


o^ 


CO 


e! 


o 


^ 


rr 


CO 


vO 


in 


o^ 


^f 


00 


<M 


r~ 





0) 


o 


^ 






CO 




"* 


^ 


(M 


C- - 






U 


CO 














rH • >. 




1—1 


1—1 






























03 


o 


r- 


1— 1 


o 


O 


00 


f-H 


r- 


i— 1 


00 • 


i> 


r—< 


<L> 


o 


^ 


(M 


<M 


r- 


i ^ 


<\] 


o • . 


vD 


vO 


o 


. o . 

s 


2 


o 


r\j 






■». 




■ - pr >' 


» 00 


■ '>-* 


o^ 


•cxa 


, . 
























r- 1 


O 


00 


O^- 


t^- 


o^ 


o^ 


vO 


00 


•00 


NO 


r^ 


<D 




o 


o 






^r 




in 


CO 


.^° 


o 


^ 


"'O 




o 


r-H 










r-rt 


^o . 




^ 


rq 


3 



4-> d> 

o 

o o^ 

CO 



&■; 






o o 

« I 

o o 



C-12 



H 




W 




W 




In 




o 




o 




o 
in 




Q 
2 


g 


<1 




H-4 


o 
o 


< 


o 


N 


^ 


i— i 




J 




i— t 


o 


pq 


o 

o 


<J 


CO 


H 




co 


o" 

O 

o 


o 




a 


© 

o 


ri 


o 





1-1 


Ph 


Eh 


Q 





W 




CO 
ED 


H 


H 





£> 


£ 





W 


trj 


J 





a 







W 


a 


9 


tf 


w 





u 


h 


H 


W 


<1 


H 


W 


< 


z 


§ 




H 




CO 




W 




H 




w 




O 




u 







o 


<Q 


o 


o 


SO 


oo 


<M 


o 


00 


CO 


r- 


o 


. 


„ 


„ 


in 


r*- 


1— I 


m 




in 


"* 


po 



o 


in 


i—i 


vO 


CO 


•^ 


o 


r^ 


CO 


m 


eg 


CO 


<* 


CO 


o 


CO 


xO 


^ 


"^ 


o> 


o 


o 


CO 


on 




PO 


in 


o 


in 


■^ 




po 




PO 




^ 



m 


PO 


vO 


o 


(M 


o 


fM 


,_, 




f\l 


CO 




o 






"tf 


vO 


O 








o 


r- 


o 


r» 


in 


m 


O 


in 


m 


^ 


vO 


r- 




(M 


nO 


"* 








rg 


m 


00 

rg 


'Sf 


CO 



"tf 


o 




^ 


r^- 


in 


— ( 


^ 


o 


O 


o 


o 


in 


in 


(M 


«o 


nO 


o 


sO 


r- 


^ 


(M 


r*~i 


nO 


in 


^H 


00 


o 


sO 




sO 


(M 


on 


(NJ 


(M 
rM 



O- 


r- 


CO 


O 


"* 


^ 


CO 


m 


in 


i-H 


<tf 


o 


(NJ 


<tf 


vO 


CO 


co 


NO 


CO 


CO 


vO 


ON 


m 


i— i 


^ 


SO 


•* 


m 


On 


t 


■>* 


r- 


^ 


■* 


co 




ON 


T-i 


- 





(NJ 


r- 


sO 


o 


in 


t^ 


(M 


PO 


m 




ON 


i— ( 


o 


^ 


o 


in 


^ 


ON 


(M 


*-H 


NO 


o 


o 


o 


ON 


ON 


00 


sO 


iM 


^r 


PO 


vO 


■sO" 


<M 


r~ 


o 




<M 


—I 




-* 




in 




vO 























n 










4- 












o 




a 

o 

u 






3 

CO 










9} 
O 


[X| 

Oh 


V 






-. 


08 




TrS 






«H 






T1 







<u 


fl 


ol 


in 


n) 







to 




"8 


4-> 

d 

1 




6 

PO 







H 


73 




H 


in 


w 



u 


U 

00 


oh 


4) 


£ 


S 








<+H 


rrt 




rt 


d 


-u 


0) 


A-f 




« 









0) 


fl; 


o< 


rt 


n 


U 




> 




u 





> 


J 


W 


>S 


u 


>! 




o 




Vk 


H 


<; 



C-13 



h 

O 
10 

H 

a 
z 
w 

w 

o 

S3 

o 

h 

W 
H 



< 
H 

10 

W 

o 
o 

Q 
H 

H 
P 

o 
Pi 
o 

< 



co 


o 


o 


o 


CNJ 


o 


i—i 


o 


r— 1 


O 


CO 


rH 


o 


o 


o 


m 


en 


■«# 


00 


ro 


e'- 


ro 


■* 


in 


CO 


o 


in 


< 


in 


er- 


sO 


<tf 


in 


rH* 


vO 


r-~ 


^ 




* 


i-H 


o 




t>- 


^ 


'—* 


^r 


sO 






I-< 






CM 




CO 




CO 







CO 

m 


CO 


o 


o 


,-H 


in 


sO 


o 


vO 


00 


O 

o 


I— 4 


sJD 


o 


CO 


ro 


n£> 


m 


i— I 




00 


o 


CO 


o 


CO 


^ 


vO 


oo 


in 




o 




















<*l 


o 


o 


CO 


^ 


^o 


O^ 


in 


CO 


o^ 




CO 


00 


r*- 




CT- 


tM 


ro 


CO 


m 












'- 




CM 




CO 







00 


vO 


ro 


o 


o 


oo 


CO 


CO 


o 


o 


o-> 


CO 


in 


nO 


o 


•> 


« 


« 


" 



o 
m 


03 

co 


00 

co 
o^ 


o 

CO 


CO 


cr- 


CO 


Cxi 





o 


o 


vO 


o 


o 


o 


00 


t- 


o 


o 


vO 


vD 


sO 


o 



00 00 CO i 



m 


oo 


m 


o 


o 


i-i 






■<*< 


m 


CO 







ft 

W 





d 

A) 


d 


cd 


m 




s 


o 








• H 


o 




•H 

•h 


co. 




H 


0) 




£j 




^J 


V 


£ 


•i-i 




Jn 




CD 


^> 




0) 


flj 


f H 







> 


2 


o 


3 








CX 


__, 


xO 


o 


vO 


co 


o^ 


CT- 


CO 


^ 


r- 


o 


in 


o 


m 


O 
CT- 


00 




o 


CO 


CO 


CO 


vO 


O^ 


CO 


CO 

ro 


CO 


in 
r- 


^ 


M3 

00 


rO 



C-14 



H 
W 




W 




fc 




o 


2 


o 


o 


o 


h-i 


m 


H 


Q 




< 


3 






o 


m 


o 
o 


< 

H 

CO 


o 


W 


o 


J 


o 

CO 


O 

s 


o 


PCj 


o 





o 

IN] 


h 


„ 


P 


o 
o 
o 


H 

CO 


Ph 


H 





£ 




W 


co 





X 


<J 


H 



3 


2 




a 


Q 
2 




< 


w 




J 


W 


o 


H 


EG 




ti 








Eh 


Cn 


£ 




w 


w 


Cm 


H 




<J 


H 


3 




H 

CO 

W 


2 

w 
u 


H 




CO 









U 





00 ° S 2 

pj qs rg -^ 



« °° ^ s 

in r^ o o 

00 "«J4 oo o 

o o £ <* 

co ^ f*" 



CO 


v£> 


(M 


o 


sO 


CO 


^F 


O 


co 


CO 


CO 


o 


in 


o 


vO 


<tf 


O 


in 


■^o 


o 


IN] 


f\J 


sO 


co" 


o" 


-tf 


CO 


co" 


vO 


•*" 


co" 


■* 


•* 




o 


r— i 


c\] 


i-H 










1-1 




1—1 





O^ 


f-l 


vO 


O 


vO 


CO 


^ 


r%! 


sO 


t^ 


CO 
CO 


<tf 


r- 


O 


in 


in 


i—i 


CO 


^ 


CO 


CO 


o 


CO 


o 


•-i 


CM 


in 


r- 






















o 


c> 


■* 


CO 


CO 


t— i 


o^ 


O 


O 


o 


^ 


<M 


(M 




vO 




t<- 


■-' 


CO 





O^ 


o 


vO 


o 


in 


sO 


1—1 


_ 


o^ 




r^ 


o 


o 




■^ 


-* 


sO 


m 


v£> 


o 


o 


o 


cr- 


sO 


CO 


^ 


co 


CO 


vO 


<tf 


o 

CO 


Tf 



53" 


d 






2 


0> 


o 






i 


<0 


•i-i 






0) 




n5 






CO 


<U 


O 




^ 


o8 


M-4 


CO 


C! 
CD 

a 


CI 


4-> 


o 


a 


1) 


CO 


•H 


"So 


f 


4) 


•rH 


0) 


cr 


<rJ 


U 


O 


J 


W 


3 


U 


s 



C-15 



H 




w 




w 




h 




o 




o 




o 




LD 




Q 




2 




< 




o 




o 




o 




^ 




o 


Q 


o 


W 


o 


s 


on 






3 


o 


a 


o 


w 


o 


et{ 


ro 






S3 


O 





o 




o 


H 


>-H 


<J 


Eq 


N 


O 


3 






w 


« 


X 


<; 


H 


H 





tn. 




w 
o 


w 


m 







z 


rf 




O 




to 




w 




H 




<1 




§ 




H 




W 




W 




H 




w 




O 




u 





^ 


"* 


\0 


o 


<* 


CO 


(M 


_ 


-* 


o 


PO 


o 


CO 


CO 


r- 


.— i 


00 


(NJ 




<tf 


m 


^r 


o 


o 


r~( 


(NJ 


00 


-* 


xO 


On 


xO 


CO 


-t 


in 


O 




CJN 


(NJ 


cm 

Cxi 


CO 



•^f 


<M 


CO 


o 


■xt< 


IT) 


On 


^ 


^ 


CO 


o 


o 







(NJ 


CM 


"* 


^ 


r- 


o 


xO 


"* 


CO 


rM 


CO 


m 


xO 


<tf 


^ 


© 


■* 


CO 


N 


m 


xO 




CO 


<NJ 


m 


M 



cm 


_ 


o 


o 


ro 


r\J 


in 


i-H 


M 


co 


xO 


o 


i— i 


xO 


r- 


xO 


•^ 


in 


CO 


X© 


<tf 


xO 


o 


m 


r- 


r\3 


o 


m 


^ 


ro 


r- 


<tf 


1-1 


oa 


^ 




CO 


1-1 


Qn 


r " H 






CO 


CO 


O 


m 


xO 


rH 


_H 


^ 


CO 


oo 


o 


r- 


CT^ 


r- 


co 


0> 


r- 


On 


co 


CTn 


CO 


00 


ON 


co 


rg 


o 


CO 


in 


o 


fj 


IN- 




fH 


rvi 




<* 




m 





nO 


(NJ 


00 


o 


nO 


fNj 


00 


v0 


T( 


in 


T' J 


o 


"tf 


nO 


o 


o 


CO 


m 


op 


o 


f- 


ON 


r- 


T 


CO 


in 


r^ 


CO 


Qn 


rvi 


(M 


CO 





o 


CO 


o 


ON 




„ 


(NJ 


ON 


m 


m 




CNl 





in 


in 


o 




n 


■xf 


CO 


■* 


























, , 




















o 




O 
















<u 


h 

^ 


- : ^ 


















'o 

m 


Oh 





<D 




















1 — 1 


P< 










in 






VH 


-(-> 





o 




rt 


ri 


rt 




O 


CO 




o 


B 

Ph 
■ H 


[id 

03 


S 

co 


o 
tq 




H 






Eh 


^5- 
m 


o 
U 

i-H 
(t) 


U 
60 


e! 







0) 


rQ 




<u 




"o 




0) 


<D 


a 1 


ro 


(H 


o 




> 




u 


o 


> 


J 


W 


s 


u 


2 




O 




Ph 


H 


< 



C-16 



3 O 

£ o g 



Q -Q 




(}33j) 9IOH jo q;§u3T 



C-17 



GLOSSARY OF TERMS 



Bent sub: 



(1) A short sub (section of drill rod) that has its 
upper thread cut concentric with the axis of 
the sub body, and its lower thread cut con- 
centric with an axis at an angle (from 1/2° 
to 3 ) in relation to the axis of the upper 
thread. 



(2) A short section of drill rod with a bend (usually 
of 1/2 to 3 ) in it, used on an in- hole motor 
to change the direction in which the hole is 
being drilled. 



Competent rock: Rock which is able to maintain an underground 

opening or a steep slope at the surface without 
artificial support. 



Core hole 8; 



A hole which has been drilled using a core drilling 
technique. 



Deflection tools: Any instrument used in the hole to purposely change 

the direction of drilling. 

Deviate the hole: To cause a change in the direction that a hole is 

being drilled. 



Dogleg: 



A sharp, undesirable change in direction of the 
hole. 



Drill string: 



The sectionalized rod or pipe connecting the drill 
bit with the surface. Used for the transmission of 
force, torque, fluid, and control. 



Fulcrum effect: A technique used to cause the drilling assembly 

to build angle (curve the drilling trajectory up) 
or lose angle (curve the drilling trajectory down) 
by establishing a pivot point on the drilling 
assembly (with a stabilizer or reamer, etc. ) and 
adding weight either ahead of or behind the pivot 
point. (See Section 6. 4. 2) 



Go-deviling: 



The process of transferring an object through 
a drill string (or pipe) by fluid flow. 



Gouge: 



Crushed and comminuted rock formed by grinding 
action between moving adjacent walls of a fault. 



Guidance: 



Combined actions of survey and steering to 
effect control of the borehole direction. 



Incompetent rock: 



Rock which is not capable of remaining standing 
in an underground opening or a steep slop© at 
the surface without artificial support. 



Jet bits: 



A bit utilizing the principle of the hydraulic jet 
to deviate holes in soft ground. (Also called 
"one-eye" bit) 



Kick sub: 



A hydraulically actuated bent sub used in 
hole deviation. 



Knuckle joint: 



A tool used to deviate holes; basically a pilot 
reamer with a universal joint principle built 
into its connection with the drill stem. 



Mud: 



Drilling fluid (it contains necessary solid 
particles and other additives to achieve desired 
results). 



Mud pump: 



The pump that injects the drilling fluid into the 
drill string at the desired rate and pressure. 



Mule shoe: 



A specially shaped cam which is designed to mate 
with a similar cam and remotely force survey 
instruments to rotate into proper angular alignment 
with respect to a reference point near the end of 
the drill string. 



Overshot: 



A wire line, self-engaging device which attaches 
itself to the head of any down-hole tool which has 
been equipped for that purpose. 



Positive displacement A motor which converts the pressure of a fluid 
motor: to shaft torque. 



Raise boring: 



A shaft drilling procedure in which a large drilling 
head is pulled back through a pilot drill hole. 



Rat hole: 



A section of hole which is purposely undersized 
(a pilot hole). Rat hole also refers to a hole of 
reduced size in the bottom of the regular well bore. 
Sometimes the driller "rat holes ahead" to facilitate 
the taking of a drill stem test when it appears that 
such tests will be desirable. 



Reverse circulation: 



A drilling fluid circulation technique in which the 
drilling fluid is pumped into the hole through an 
annular area, either outside the drill string or 
enclosed by a double tube configuration, and 
returns up the center of the drill string. 



Spudding bit: 



A spade shaped bit used to deviate holes in soft 
ground. 



Steering: 



The mechanical process of directing a borehole 
along a desired path. 



Slim-hole: 



A bore hole of small diameter which can be drilled 
with a very light -duty rig. 



Stinger: 



The lower drilling assembly consisting of a bit 
and reamer. 



Sub: 

Survey: 



A very short section of drill string. 

The process of determining the path of a borehole 
relative to a fixed point in space by determination 
of attitudes in two dimensions and distance in the 
third at a sequence of stations. The line segments 
between stations are then connected to form a two- 
dimensional plot of the survey. 



Tool: 



Any ancillary device used to assist in drilling 
operation. 



Turbine; 



An engine or motor driven by the movement of 
water, steam, air, etc. past the vanes of a wheel 
or set of wheels fastened to a driving shaft. The 
turbine converts fluid velocity to shaft torque. 



Whipstock: 



A wedge shaped tool used to change the direction 
of drilling. 



REFERENCES 



1. Business Week, "The Move to Save Methane", January 20, 1975, 
p. 3 0L. 

2. Foster, Dr. Eugene L. , A Preliminary Appraisal of the Relative 
Construction Costs of Pilot Tunnels vs. Long Horizontal Bore 
Holes . Underground Technology Division, Foster-Miller Associates, 
Inc., Alexandria, Virginia, June 3 0, 1975. 

3. "A New Sensing System for Pre-Excavation Sursurface Investigation 
for Tunnels in Rock Masses", a study in progress for Federal 
Highway Administration, Contract FH-11-8602, ENSCO, Inc., 
Springfield, Va. . 

4. Ash, J.- L; Russell, B. E. , and Rommell, R. R; , Improved 
Subsurface Investigation for Highway Tunnel Design and Construction 
Vol. 1, Subsurface Investigation System Planning . Report for 
Federal Highway Administration, Contract DOT-FH- 11-8036, 

Fenix and Scisson, Inc. , Tulsa, Okla. May, 1974. 

5. Kitamura , I., Executive Director, Japan Tunneling Association. 
Letter to William Ae Ribich, Foster-Miller Associates, Inc. , Subject 
Horizontal Long Hole Drilling on Seikan Tunnel, October 3 0, 1974. 

6. Lummus, James L. , "Drilling Economics", Petroleum Engineer , 
October, 1974, pp. 120-126. 

7. Brekke, T. L. and Howard, T. R. , Functional Classification of 
Gouge Materials from Seams and Faults in Relation to Stability 
Problems in Underground Openings. Report for Advanced Research 
Projects Agency, Contract H02 10023, University of California, 
Berkley, March, 1972. 

8. Paone, James, Bruce, William E. , and Morrell, Roger J. , 
Horizontal Boring Technology; A State -of- the -Art Study, U* S. 
Bureau of Mines Information Circular 83 92, September, 1968. 

9. Williamson, T. N. Research in Long Hole Exploratory Drilling 

for Rapid Excavation Underground. Report for Advanced Research 
Projects Agency, Phase I, Contract H0210037, Jacobs Assoc, 
San Francisco, Calif. , April, 1972. 

10. Williamson, T. N. , Research in Long Hole Exploratory Drilling 
for Rapid Excavation Underground, Report for Advanced Research 
Projects Agency, Phase II, Contract H0220020, Jacobs Assoc. , 
San Francisco, Calif. , October, 1972. 

11. Rommell, Robert R. and Rivers, Larry A., Advanced Techniques 
for Drilling 1, 000 ft. Small Diameter Horizontal Holes in a 

Coal Seam, - Report for U.S. Bureau of Mines, Contract H0111355, 
Vol. 1, Fenix and Scisson, Inc., Tulsa, Okla. March, 1973. 



12. Williamson, T. N. , "Probe Drilling for Rapid Tunneling", 
Proceedings of First North American Rapid Excavation and 
Tunneling Conference (Chicago, 1972. ) AIME, New York 
1972, pp. 65-87. 

13. Drilling with Diamonds, An Overview , Christensen Diamond 
Products, Salt Lake City, Utah. 

14. (a) Chisholm, Donald, Vice President, Longyear Co. , Letter 
to John C. Harding, Foster -Miller Associates, Inc. , Subject 
Long Horizontal Core Holes, October 28, 1974. 

(b) Anderson, R. , Casper, R. , Chisholm, D. , Doolan, J. , 
Miller, J. , and Swensen, W. , Longyear Co. , Conference with 
Foster-Miller Associates personnel, Minneapolis, Minn. , 
December 10, 1974. 

15. McLerran, A. R. , NSF Field Project Officer, Deep Sea Drilling 
Project. Letter to E. J. Goldman, Foster-Miller Associates, 
Inc., June 11, 1974, Subject - Roller Bit Coring. 

16. Folwell, W. T. , "Raise Borers Applied Horizontally", 
Proceedings of First North American Rapid Excavation and 
Tunneling Conference (Chicago, 1972), AIME, New York, 1972 
pp. 719-737. 

17. Bruner, T. E. , "Horizontal, Small Diameter Road Borings in 
Rock ", Proceedings of the Rapid Excavation and Tunneling 
Conference (San Francisco, 1974) , AIME, New York, 1974, 
pp. 229-247. 

18. Hughes Blast Hole Bits, Catalog No. 106, Hughes Tool Co. , 
Houston, Texas, 1973. 

19. Hughes Tool Company, Personnal Communication, April, 1974. 

20. FS-400, Paper on Koken FS-400 Horizontal Boring Machine, 
Koken Boring Co. , Ltd. , Tokyo, Japan. 

21. McGregor, K. , The Drilling of Rock (London: CR Books 
Ltd., 1967). 

22. Dyna-Drill Handbook, Second Edition, Dyna-Drill Division of 
Smith International, Inc. , Long Beach, Calif. 

23. Mochida, Yutaka, "Long Horizontal Boring", Permanent Way 
(Japan) Vol. 14, No. 3, April, 1973, pp. 5-11. 

24. Tanaka, Tomoharu, "Seikan Undersea Tunnel", Civil Engineering 
in Japan, Japan Society Civil Engineers, 1970, pp. 7 1 - 81. 



25. Emery, M. M. , "Field Report - Dyna-Drill Co., - Division of 
Smith International, Inc. ", June 21, 1972. 

26. McCollum, Jay D. , Domestic Sales Manager, Dyna-Drill Co. , 
Letter to Henney, Shell Pipe Line Corp. , Subject - Application 
of the Dyna-Drill in Controlled Directional Horizontal Drilling, 
June 15, 1973. 

27. Cobbs, J. H. , and L. R. Reeder, Shaft Drilling State of the Art , 
Report for U. S. Bureau of Mines, Contract S0122047, James 

H. Cobbs, Engineering, Tulsa, Okla. , March, 1973. 

28. Kitamura, I. , Executive Director, Japan Tunneling Association 
Letter to William A. Ribich, Foster-Miller Associates, Inc. , 
Subject - Horizontal Long Hole Drilling on Seikan Tunnel, 
December 20, 1974. 

29. Goode, Richard, U. S. Atomic Energy Commission and 
Waltman, F. D. , Fenix and Scisson, Inc. , Conference with 
Foster-Miller Associates personnel, A. E. C. Test Site, Mercury, 
Nevada, October 10, 1974. 

3 0. Melaugh, John F. , Directional Pilling; A Survey of the Art 

and the Science, May, 1970. 

31. (a) Knapp, S. R. , 'Are We Missing the Cheapest Solution to 

our Crooked-Hole Problem? " The Oil and Gas Journal , 
June 19, 1961, pp. 103, 106, 108. 

(b) Knapp, S. R. , "Bit Geometry as Related to Hole Deviation 
Mechanics", Drilling , May, 1965, pp. 34-37, 39. 

(c) Knapp, S. R. , "Solutions to Crooked Hole Problems Possible", 
The Drilling Contractor , January- February, 1967, pp. 43-46, 48, 
50, 54, 60. 

3 2. Davis, Ira, General Manager, Directional Drilling, Wilson 

Downhole Services, Houston, Texas, Conference on Directional 
Drilling, Massachusetts Institute of Technology, Cambridge, 
Mass. January 15, 1975. 

33. Humphrey, Inc. , Personnal Communication, December 6, 1974. 

34. Brantly, J. E. , Rotary Drilling Handbook, (New York; Palmer 
Publications, 1961). 

35. (a) Sims, Darrell L. and Wiley, T.J. Jr., Drill String. Drill 
Pipe, Bumper Subs, Drill Collars, Coring Equipment. Prepared 
for National Science Foundation Under Contract NSF C-482. 
NTIS No. PB 212-133. April, 1972. 



(b) Larson, V. F. and Wiley, T. J. Jr. , Deep Sea Drilling Project , 
Technical Report No. 6. Core Bits , Prepared for National Science 
Foundation Under Contract NSF C-482. ' NTIS No. PB-232-159. 
April, 1974. 



36. Wilson, J. W. , and P. C. Graham, "Boring at High Thrust and 

its Potential in the Hard- Rock Mining Industry in South Africa", 
Proceedings of the Rapid Excavation and Tunneling Conference 
(San Francisco, 1974) AIME, New York, 1974, pp. 1053-1071. 

3 7. Simpson, Jay, Drilling Fluids and Environments . Presented at 

the Workshop of the Ad Hoc Committee on Technology of Drilling 
for Energy Resources, National Research Council, National 
Assembly of Engineering, Park City, Utah, June 25-27, 1975. 



BIBLIOGRAPHY 



1. Ash, J. L. Russell, B. E. , and Rommell, R. R. , Improved 
Subsurface Investigation for Highway Tunnel Design and Construction 
Vol. 1, Subsurface Investigation System Planning. Report for 
Federal Highway Administration, Contract DOT-FH- 11-8036, ' 
Fenix and Scisson, Inc. , Tulsa, Okla. May, 1974. 

2. Brantly, J. E. , Rotary Drilling Handbook , (New York: Palmer 
Publications, 196~1T 

3. Brekke, T.L. and Howard, T. R. , Functional Classification of 
Gouge Materials from Seams and Faults in Relation to Stability- 
Problems in Underground Openings. Report for Advanced Research 
Projects Agency, Contract H02 10023, University of California, 
Berkley, March, 1972. 

4. Bruner, T. E. , "Horizontal, Small Diameter Road Borings in 
Rock", Proceedings of the Rapid Excavation and Tunneling 
Conference (San Francisco, 1974) AIME, New York, 1974, 
pp. 229-247. r 

5. Business Week, "A New Way to Keep Oil Drills on Track", 
March 3, 1975, pp. 28B and 28D. 

6. Business Week, "The Move to Save Methane", January 20, 1975, 
p. 3 0L. 

7. Cobbs, J. H. , and L. R. Reeder, Shaft Drilling State of the Art , 
Report for U.S. Bureau of Mines, Contract S0122047, James 
H. Cobbs, Engineering, Tulsa, Okla. , March, 1973. 

8. Cumming, James D. , Diamond Drill Handbook (Toronto, Ontario: 
J. K. Smith & Sons Diamond Products Limited, 1975). 

9. Deul, Maurice and Kim, Ann G. , Degasification of Coal beds -- 
A Commercial Source of Pipeline Gas. Presented at the 
Symposium on Clean Fuels from Coal, II. Institute of Gas 
Technology, Chicago, 111. , June 22-27, 1975. 

10. Dowding, Charles H. , Horizontal Drilling Potential. Emphasis; 
Soft Ground. Prepared for the Workshop of the Ad Hoc Committee 
on Technology of Drilling for Energy Resources, National Assembly 
of Engineering, Park City, Utah, June 25-27, 1975. 

11. Drilling with Diamonds, An Overview , Christensen Diamond 
Products. Salt Lake City, Utah. 



12. Dyna-Drill Handbook, Second Edition, Dyna-Drill Division of 
Smith International, Inc. Long Beach, Calif. 

13. Fields, H. H. , Perry, J. H. , and Deul, M. , Commercial - 
Quality Gas From a Multipurpose Borehole Located in the 
Pittsburgh Coalbed. , Bureau of Mines Report of Investigation 
8025, 1975. 

14. Folwell, W. T. , "Raise Borers Applied Horizontally", 
Proceedings of First North American Rapid Excavation and 
Tunneling Conference (Chicago, 1972) , AIME, New York, 1972 
pp. 719-737. 

15. Foster, Dr. Eugene L. , A Preliminary Appraisal of the Relative 
Construction Costs of Pilot Tunnels vs. Long Horizontal Bore 
Holes. Underground Technology Division, Foster-Miller 
Associates, Inc., Alexandria, Virginia, June 30, 1975. 

16. FS-400, Paper on Koken FS-400 Horizontal Boring Machine, 
Koken Boring Co. , Ltd. , Tokyo, Japan. 

17. Garrison, E. Pope, Direction Drilling and Down-Hole Motors. 
Presented at the Workshop of the Ad Hoc Committee on Technology 
of Drilling for Energy Resources, National Research Council, 
National Assembly of Engineering, Park City, Utah, June 25-27, 1975. 

18. Garrison, E. P. , Down-Hole Motors . Presented at the Workshop 
of the Ad Hoc Committee on Technology of Drilling for Energy 
Resources, National Research Council, National Assembly of 
Engineering, Park City, Utah, June 25-27, 1975. 

19. Heilhecker, Joe, Telemetry, Drill- Stem Problems, and Hole 
Control. Presented at the Workshop of the Ad Hoc Committee 

on Technology of Drilling for Energy Resources, National Research 
Council, National Assembly of Engineering, Park City, Utah, 
June 25-27, 1975. 

20. Hughes Blast Hole Bits, Catalog No, 106, Hughes Tool Co. , 
Houston, Texas, 1973. 

21. (a) Knapp, S. R. , "Are We Missing the Cheapest Solution to 
our Crooked-Hole Problem? " T he Oil and Gas Journal , 
June 19, 1961, pp. 103, 106, 108. 

(b) Knapp, S. R. , "Bit Geometry as Related to Hole Deviation 
Mechanics", Drilling , May, 1965, pp. 3 4-3 7, 3 9. 

(c) Knapp, S. R. , "Solutions to Crooked Hole Problems Possible", 
The Drilling Contractor , January - February 1967, pp. 43-46, 

48, 50, 54, 60. 

22. Larson, V. F. and Wiley, T. J. Jr. , Deep Sea Drilling Project , 
Technical Report No. 6. Core Bits , Prepared for National Science 
Foundation Under Contract NSF C-482. NTIS No. PB-232-159. 
April, 1974. 



23. Lummus, James L. , "Drilling Economics", Petroleum Engineer , 
October, 1974, pp. 120-126. 

24. Maurer, William C. , Novel Drilling Techniques (London: 
Pergamon Press, 1968). 

25. McGregor, K. , The Drilling of Rock (London; CR Books 
Ltd. , 1967). 

26. Me laugh, John F. , Directional Pilling; A Survey of the Art 
and the Science, May, 1970. 

27. Mochida, Yutaka, "Long Horizontal Boring", Permanent Way 
(Japan) Vol. 14, No. 3, April, 1973, pp. 5-11. 

28. Paone, James, Bruce, William E. , and Morrell, Roger J. , 
Horizontal Boring Technology; A State -of- the -Art Study, U. S. 
Bureau of Mines Information Circular 83 92, September, 1968. 

29. Rommell, Robert R. and Rives, Larry A., Advanced Techniques 
for Drilling 1, 000 ft. Small Diameter Horizontal Holes in a 

Coal Seam, Report for U.S. Bureau of Mines, Contract H0111355, 
Col. 1, Fenix and Scisson, Inc. , Tulsa, Okla. March, 1973. 

3 0. Simpson, Jay, Drilling Fluids and Environments. Presented at the 

Workshop of the Ad Hoc Committee on Technology of Drilling for 
Energy Resources, National Research Council, National Assembly 
of Engineering, Park City, Utah, June 25-27, 1975. 

3 1. Sims, Darrell L. and Wiley, T. J. Jr. , Drill String. Drill Pipe , 

Bumper Subs, Drill Collars, Coring Equipment. Prepared for 
National Science Foundation Under Contract NSF C-482. NTIS 
No. PB 212-133. April, 1972. 

32. Tanaka, Tomoharu, "Seikan Undersea Tunnel", Civil Engineering 
in Japan, Japan Society Civil Engineers, 1970, pp. 71-81. 

33. Wahlstrom, Ernest E. , Tunneling in Rock (Amsterdam; Elsevier 
Scientific Publishing Co., 1973). 

34. Williamson, T.N. Research in Long Hole Exploratory Drilling 

for Rapid Excavation Underground. Report for Advanced Research 
Projects Agency, Phase I, Contract H0210037, Jacobs Assoc. , 
San Francisco, Calif. , April, 1972. 

3 5. Williamson, T. N. , Research in Long Hole Exploratory Drilling 

for Rapid Excavation Underground, Report for Advanced Research 
Projects Agency, Phase II, Contract H0220020, Jacobs Assoc. , 
San Francisco, Calif. , October, 1972. 



36. Williamson, T. N. , "Probe Drilling for Rapid Tunneling", 

Proceedings of First North American Rapid Excavation and 
Tunneling Conference (Chicago, 1972) . A]ME, New York, 
1972, pp. 65-87 

3 7. Wilson, J. W. , and P. C. Graham, "Boring at High Thrust and 

its Potential in the Hard- Rock Mining Industry in South Africa" 
Proceedings of the Rapid Excavation and Tunneling Conference 
TSalT Frangisco, lW rAlM^, New Vork, 1974. pp. 1053-1071. 



DOT LIBRARy 



m. 



FHWA 



R&D